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securityvulnsSecurityvulnsSECURITYVULNS:DOC:21527
HistoryMar 26, 2009 - 12:00 a.m.

Cisco Security Advisory: Cisco IOS Software Multiple Features Crafted TCP Sequence Vulnerability

2009-03-2600:00:00
vulners.com
40
JSON

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Cisco Security Advisory: Cisco IOS Software Multiple Features Crafted
TCP Sequence Vulnerability

Advisory ID: cisco-sa-20090325-tcp

http://www.cisco.com/warp/public/707/cisco-sa-20090325-tcp.shtml

Revision 1.0

For Public Release 2009 March 25 1600 UTC (GMT)

Summary

Cisco IOS Software contains a vulnerability in multiple features
that could allow an attacker to cause a denial of service (DoS)
condition on the affected device. A sequence of specially crafted TCP
packets can cause the vulnerable device to reload.

Cisco has released free software updates that address this
vulnerability.

Several mitigation strategies are outlined in the workarounds section
of this advisory.

This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20090325-tcp.shtml

Note: The March 25, 2009, Cisco IOS Security Advisory bundled
publication includes eight Security Advisories. All of the advisories
address vulnerabilities in Cisco IOS Software. Each advisory lists
the releases that correct the vulnerability or vulnerabilities in the
advisory. The following table lists releases that correct all Cisco
IOS Software vulnerabilities that have been published in Cisco
Security Advisories on March 25, 2009, or earlier.

http://www.cisco.com/warp/public/707/cisco-sa-20090325-bundle.shtml

Individual publication links are listed below:

Affected Products

Vulnerable Products
±-----------------

Devices running affected versions of Cisco IOS Software and Cisco IOS
XE Software are affected when configured to use any of the following
features within Cisco IOS:

  • Airline Product Set (ALPS)
  • Serial Tunnel Code (STUN) and Block Serial Tunnel Code (BSTUN)
  • Native Client Interface Architecture support (NCIA)
  • Data-link switching (DLSw)
  • Remote Source-Route Bridging (RSRB)
  • Point to Point Tunneling Protocol (PPTP)
  • X.25 for Record Boundary Preservation (RBP)
  • X.25 over TCP (XOT)
  • X.25 Routing

Information on how to determine whether an affected feature is
enabled on a device are provided in the Details section of this
advisory.

To determine the Cisco IOS Software release that is running on a
Cisco product, administrators can log in to the device and issue the
"show version" command to display the system banner. The system
banner confirms that the device is running Cisco IOS Software by
displaying text similar to "Cisco Internetwork Operating System
Software" or "Cisco IOS Software." The image name displays in
parentheses, followed by "Version" and the Cisco IOS Software release
name. Other Cisco devices do not have the "show version" command or
may provide different output.

The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.3(26) with an installed image name of
C2500-IS-L:

Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by cisco Systems, Inc.
Compiled Mon 17-Mar-08 14:39 by dchih

<output truncated>

The following example shows a product that is running Cisco IOS
Software Release 12.4(20)T with an image name of
C1841-ADVENTERPRISEK9-M:

Router#show version
Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Thu 10-Jul-08 20:25 by prod_rel_team

<output truncated>

Additional information about Cisco IOS Software release naming
conventions is available in "White Paper: Cisco IOS Reference Guide"
at the following link: http://www.cisco.com/warp/public/620/1.html .

Products Confirmed Not Vulnerable
±-------------------------------

The following product and feature have been confirmed not vulnerable:

  • Cisco IOS XR Software
  • BGP is not affected

No other Cisco products or features configured within Cisco IOS
Software are currently known to be affected by this vulnerability.

Details

Completion of the 3-way handshake to the associated TCP port number
(s) of any of the features outlined below is required in order for
the vulnerability to be successfully exploited.

Airline Product Set (ALPS)
±------------------------

Devices configured for ALPS are vulnerable. The default TCP listening
ports for ALPS are 350 and 10000. The following example shows a
vulnerable ALPS configuration:

alps local-peer <ip address>

Further information about ALPS is available in "Cisco IOS Bridging
and IBM Networking Configuration Guide, Release 12.2 - Configuring
the Airline Product Set" at the following link
http://www.cisco.com/en/US/docs/ios/12_2/ibm/configuration/guide/bcfalps_ps1835_TSD_Products_Configuration_Guide_Chapter.html

Serial Tunnel Code (STUN) and Block Serial Tunneling (BSTUN)
±----------------------------------------------------------

Devices configured for either STUN or BSTUN are vulnerable. The
default listening TCP ports for STUN are 1990,1991 1992 and 1994. The
default listening TCP ports for BSTUN are 1963, 1976, 1977, 1978 and
1979 The following example shows a vulnerable STUN configuration:

interface serial 0/0/0
encapsulation stun

The following example shows a vulnerable BSTUN configuration:

interface serial 0/0/0
encapsulation bstun

Further information about STUN and BSTUN is available in "Cisco IOS
Bridging and IBM Networking Configuration Guide, Release 12.2 -
Configuring Serial Tunnel and Block Serial Tunnel" at the following
link
http://www.cisco.com/en/US/docs/ios/12_2/ibm/configuration/guide/bcfstun_ps1835_TSD_Products_Configuration_Guide_Chapter.html

Native Client Interface Architecture support (NCIA)
±-------------------------------------------------

Devices configured for NCIA are vulnerable, because of the underlying
transport they will use. The default listening TCP ports will be
dependent on the protocol used with NCIA, such as RSRB or DSLw. The
following examples shows a vulnerable configuration:

ncia server 1 10.66.91.138 0000.1111.2222 2222.2222.2222 1

Further information about NCIA is available in "Cisco IOS Bridging
and IBM Networking Configuration Guide, Release 12.4 - Configuring
NCIA Client/Server" at the following link
http://www.cisco.com/en/US/docs/ios/bridging/configuration/guide/br_ncia_client_svr_ps6350_TSD_Products_Configuration_Guide_Chapter.html

Data-link switching (DLSw)
±------------------------

Devices configured for DLSw are vulnerable. The default listening TCP
ports for DSLw are 2065, 2067, 1981, 1982 and 1983. The following
example shows a vulnerable configuration:

dlsw local-peer peer-id <ip address>

Devices configured with either FST Encapsulation or Direct
Encapsulation are still vulnerable as the affected TCP ports are
opened by the "dslw local-peer peer-id ip address" command.

Further information about DLSw is available in "Cisco IOS Bridging
and IBM Networking Configuration Guide, Release 12.4 - Configuring
Data-Link Switching Plus" at the following link
http://www.cisco.com/en/US/docs/ios/bridging/configuration/guide/br_dlsw_plus_ps6350_TSD_Products_Configuration_Guide_Chapter.html

Remote Source-Route Bridging (RSRB)
±---------------------------------

Devices configured for RSRB Using IP Encapsulation over a TCP
connection are vulnerable. The default listening TCP ports for RSRB
are 1996,1987, 1988 and 1989. The following example shows a
vulnerable configuration:

source-bridge ring-group 10
source-bridge remote-peer 10 tcp <ip address>

Devices configured with either RSRB Using Direct Encapsulation or
RSRB Using IP Encapsulation over an FST Connection are not affected.

Further information about RSRB is available in "Cisco IOS Bridging
and IBM Networking Configuration Guide, Release 12.2 - Configuring
Remote Source-Route Bridging" at the following link
http://www.cisco.com/en/US/docs/ios/12_2/ibm/configuration/guide/bcfrsrb_ps1835_TSD_Products_Configuration_Guide_Chapter.html

Point to Point Tunneling Protocol (PPTP)
±--------------------------------------

Devices configured for PPTP are vulnerable. The default listening TCP
port for PPTP is 1723. The following examples shows a vulnerable
configuration:

vpdn enable
!
vpdn-group pptp
! Default PPTP VPDN group
 accept-dialin
  protocol pptp
  virtual-template 1

Or

vpdn enable
!
vpdn-group L2_Tunneling
! Default L2TP VPDN group
! Default PPTP VPDN group
 accept-dialin
  protocol any
  virtual-template 1

Further information about PPTP is available in "Cisco IOS VPDN
Configuration Guide, Release 12.4 - Configuring Client-Initiated
Dial-In VPDN Tunneling" at the following link
http://www.cisco.com/en/US/docs/ios/vpdn/configuration/guide/client_init_dial-in_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1105140

X.25 Record Boundary Preservation (RBP)
±-------------------------------------

Devices configured for RBP are vulnerable. The listening TCP port is
configured with the "local port port_number" CLI command, as shown in
the next examples. The following examples shows vulnerable
configurations. The first leverages switched virtual circuits (SVC):

interface Serial1/0
   x25 map rbp 1111 local port <port_number>

The second example, leverages a permanent virtual circuit (PVC):

interface Serial1/0
   x25 map pvc <pvc_number> rbp local port <port_number>

Further information about RBP is available in "Cisco IOS Wide-Area
Networking Configuration Guide, Release 12.4 - X.25 Record Boundary
Preservation for Data Communications Networks" at the following link
http://www.cisco.com/en/US/docs/ios/wan/configuration/guide/wan_x25_rbp_dcn_ps6350_TSD_Products_Configuration_Guide_Chapter.html

X.25 over TCP (XOT)
±-----------------

Devices configured for XOT are vulnerable. The default listening TCP
port for XOT is 1998. The following example shows a vulnerable
configuration.

xot access-group 1

and a corresponding access-list 1.

Further information about XOT is available in "Cisco IOS Wide-Area
Networking Configuration Guide, Release 12.4 - X.25 over TCP
Profiles" at the following link
http://www.cisco.com/en/US/docs/ios/wan/configuration/guide/wan_x25otcp_pro_ps6350_TSD_Products_Configuration_Guide_Chapter.html

X25 Routing
±---------

Devices configured with X25 are vulnerable. The default listening TCP
port for X25 Routing is 1998. The following example shows a
vulnerable configuration.

x25 routing

Further information about X25 is available in "Cisco IOS Wide-Area
Networking Configuration Guide, Release 12.4 - Configuring X.25 and
LAPB" at the following link
http://www.cisco.com/en/US/docs/ios/wan/configuration/guide/wan_cfg_x25_lapb_ps6350_TSD_Products_Configuration_Guide_Chapter.html

This vulnerability is documented in the following Cisco Bug ID:
CSCsr29468 and has been assigned the Common Vulnerabilities and
Exposures (CVE) identifier CVE-2009-0629.

Vulnerability Scoring Details

Cisco has provided scores for the vulnerability in this advisory
based on the Common Vulnerability Scoring System (CVSS). The CVSS
scoring in this Security Advisory is done in accordance with CVSS
version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of
the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding
CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss

CSCsr29468: Cisco IOS Software Multiple Features Crafted TCP Sequence
Vulnerability

CVSS Base Score - 7.8

Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete

CVSS Temporal Score - 6.4

Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

Impact

Successful exploitation of this vulnerability will cause the device
to reload. Repeated attempts to exploit this vulnerability could
result in a sustained DoS condition.

Software Versions and Fixes

When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center (TAC) or your contracted
maintenance provider for assistance.

Each row of the Cisco IOS software table (below) names a Cisco IOS
release train. If a given release train is vulnerable, then the
earliest possible releases that contain the fix (along with the
anticipated date of availability for each, if applicable) are listed
in the "First Fixed Release" column of the table. The "Recommended
Release" column indicates the releases which have fixes for all the
published vulnerabilities at the time of this Advisory. A device
running a release in the given train that is earlier than the release
in a specific column (less than the First Fixed Release) is known to
be vulnerable. Cisco recommends upgrading to a release equal to or
later than the release in the "Recommended Releases" column of the
table.

±------------------------------------------------------------------+
| Major | Availability of Repaired Releases |
| Release | |
|------------±-----------------------------------------------------|
| Affected | | |
| 12.0-Based | First Fixed Release | Recommended Release |
| Releases | | |
|-------------------------------------------------------------------|

There are no affected 12.0 based releases
Affected
12.1-Based
Releases
-------------------------------------------------------------------
There are no affected 12.1 based releases
-------------------------------------------------------------------
Affected
12.2-Based
Releases
------------±----------------------------±-----------------------
12.2
------------±----------------------------±-----------------------
12.2B
------------±----------------------------±-----------------------
12.2BC
------------±----------------------------±-----------------------
12.2BW
------------±----------------------------±-----------------------
12.2BX
------------±----------------------------±-----------------------
12.2BY
------------±----------------------------±-----------------------
12.2BZ
------------±----------------------------±-----------------------
12.2CX
------------±----------------------------±-----------------------
12.2CY
------------±----------------------------±-----------------------
12.2CZ
------------±----------------------------±-----------------------
12.2DA
------------±----------------------------±-----------------------
12.2DD
------------±----------------------------±-----------------------
12.2DX
------------±----------------------------±-----------------------
12.2EW
------------±----------------------------±-----------------------
12.2EWA
------------±----------------------------±-----------------------
12.2EX
------------±----------------------------±-----------------------
12.2EY
------------±----------------------------±-----------------------
12.2EZ
------------±----------------------------±-----------------------
12.2FX
------------±----------------------------±-----------------------
12.2FY
------------±----------------------------±-----------------------
12.2FZ
------------±----------------------------±-----------------------
12.2IRA
------------±----------------------------±-----------------------
12.2IRB
------------±----------------------------±-----------------------
12.2IXA
------------±----------------------------±-----------------------
12.2IXB
------------±----------------------------±-----------------------
12.2IXC
------------±----------------------------±-----------------------
12.2IXD
------------±----------------------------±-----------------------
12.2IXE
------------±----------------------------±-----------------------
12.2IXF
------------±----------------------------±-----------------------
12.2IXG
------------±----------------------------±-----------------------
12.2JA
------------±----------------------------±-----------------------
12.2JK
------------±----------------------------±-----------------------
12.2MB
------------±----------------------------±-----------------------
12.2MC
------------±----------------------------±-----------------------
12.2S
------------±----------------------------±-----------------------
12.2SB
------------±----------------------------±-----------------------
12.2SBC
------------±----------------------------±-----------------------
12.2SCA
------------±----------------------------±-----------------------
12.2SCB
------------±----------------------------±-----------------------
12.2SE
------------±----------------------------±-----------------------
12.2SEA
------------±----------------------------±-----------------------
12.2SEB
------------±----------------------------±-----------------------
12.2SEC
------------±----------------------------±-----------------------
12.2SED
------------±----------------------------±-----------------------
12.2SEE
------------±----------------------------±-----------------------
12.2SEF
------------±----------------------------±-----------------------
12.2SEG
------------±----------------------------±-----------------------
12.2SG
------------±----------------------------±-----------------------
12.2SGA
------------±----------------------------±-----------------------
12.2SL
------------±----------------------------±-----------------------
12.2SM
------------±----------------------------±-----------------------
12.2SO
------------±----------------------------±-----------------------
12.2SQ
------------±----------------------------±-----------------------
12.2SRA
------------±----------------------------±-----------------------
12.2SRB
------------±----------------------------±-----------------------
12.2SRC
------------±----------------------------±-----------------------
12.2SRD
------------±----------------------------±-----------------------
12.2STE
------------±----------------------------±-----------------------
12.2SU
------------±----------------------------±-----------------------
12.2SV
------------±----------------------------±-----------------------
12.2SVA
------------±----------------------------±-----------------------
12.2SVC
------------±----------------------------±-----------------------
12.2SVD
------------±----------------------------±-----------------------
12.2SVE
------------±----------------------------±-----------------------
12.2SW
------------±----------------------------±-----------------------
12.2SX
------------±----------------------------±-----------------------
12.2SXA
------------±----------------------------±-----------------------
12.2SXB
------------±----------------------------±-----------------------
12.2SXD
------------±----------------------------±-----------------------
12.2SXE
------------±----------------------------±-----------------------
12.2SXF
------------±----------------------------±-----------------------
12.2SXH
------------±----------------------------±-----------------------
12.2SXI
------------±----------------------------±-----------------------
12.2SY
------------±----------------------------±-----------------------
12.2SZ
------------±----------------------------±-----------------------
12.2T
------------±----------------------------±-----------------------
12.2TPC
------------±----------------------------±-----------------------
12.2XA
------------±----------------------------±-----------------------
12.2XB
------------±----------------------------±-----------------------
12.2XC
------------±----------------------------±-----------------------
12.2XD
------------±----------------------------±-----------------------
12.2XE
------------±----------------------------±-----------------------
12.2XF
------------±----------------------------±-----------------------
12.2XG
------------±----------------------------±-----------------------
12.2XH
------------±----------------------------±-----------------------
12.2XI
------------±----------------------------±-----------------------
12.2XJ
------------±----------------------------±-----------------------
12.2XK
------------±----------------------------±-----------------------
12.2XL
------------±----------------------------±-----------------------
12.2XM
------------±----------------------------±-----------------------
12.2XN
------------±----------------------------±-----------------------
12.2XNA
------------±----------------------------±-----------------------
12.2XNB
------------±----------------------------±-----------------------
12.2XNC
------------±----------------------------±-----------------------
12.2XO
------------±----------------------------±-----------------------
12.2XQ
------------±----------------------------±-----------------------
12.2XR
------------±----------------------------±-----------------------
12.2XS
------------±----------------------------±-----------------------
12.2XT
------------±----------------------------±-----------------------
12.2XU
------------±----------------------------±-----------------------
12.2XV
------------±----------------------------±-----------------------
12.2XW
------------±----------------------------±-----------------------
12.2YA
------------±----------------------------±-----------------------
12.2YB
------------±----------------------------±-----------------------
12.2YC
------------±----------------------------±-----------------------
12.2YD
------------±----------------------------±-----------------------
12.2YE
------------±----------------------------±-----------------------
12.2YF
------------±----------------------------±-----------------------
12.2YG
------------±----------------------------±-----------------------
12.2YH
------------±----------------------------±-----------------------
12.2YJ
------------±----------------------------±-----------------------
12.2YK
------------±----------------------------±-----------------------
12.2YL
------------±----------------------------±-----------------------
12.2YM
------------±----------------------------±-----------------------
12.2YN
------------±----------------------------±-----------------------
12.2YO
------------±----------------------------±-----------------------
12.2YP
------------±----------------------------±-----------------------
12.2YQ
------------±----------------------------±-----------------------
12.2YR
------------±----------------------------±-----------------------
12.2YS
------------±----------------------------±-----------------------
12.2YT
------------±----------------------------±-----------------------
12.2YU
------------±----------------------------±-----------------------
12.2YV
------------±----------------------------±-----------------------
12.2YW
------------±----------------------------±-----------------------
12.2YX
------------±----------------------------±-----------------------
12.2YY
------------±----------------------------±-----------------------
12.2YZ
------------±----------------------------±-----------------------
12.2ZA
------------±----------------------------±-----------------------
12.2ZB
------------±----------------------------±-----------------------
12.2ZC
------------±----------------------------±-----------------------
12.2ZD
------------±----------------------------±-----------------------
12.2ZE
------------±----------------------------±-----------------------
12.2ZF
------------±----------------------------±-----------------------
12.2ZG
------------±----------------------------±-----------------------
12.2ZH
------------±----------------------------±-----------------------
12.2ZJ
------------±----------------------------±-----------------------
12.2ZL
------------±----------------------------±-----------------------
12.2ZP
------------±----------------------------±-----------------------
12.2ZU
------------±----------------------------±-----------------------
12.2ZX
------------±----------------------------±-----------------------
12.2ZY
------------±----------------------------±-----------------------
12.2ZYA
------------±----------------------------±-----------------------
Affected
12.3-Based
Releases
-------------------------------------------------------------------
There are no affected 12.3 based releases
-------------------------------------------------------------------
Affected
12.4-Based
Releases
------------±----------------------------±-----------------------
12.4
------------±----------------------------±-----------------------
12.4JA
------------±----------------------------±-----------------------
12.4JDA
------------±----------------------------±-----------------------
12.4JK
------------±----------------------------±-----------------------
12.4JL
------------±----------------------------±-----------------------
12.4JMA
------------±----------------------------±-----------------------
12.4JMB
------------±----------------------------±-----------------------
12.4JX
------------±----------------------------±-----------------------
12.4MD
------------±----------------------------±-----------------------
12.4MR
------------±----------------------------±-----------------------
12.4SW
------------±----------------------------±-----------------------
12.4T
------------±----------------------------±-----------------------
12.4XA
------------±----------------------------±-----------------------
12.4XB
------------±----------------------------±-----------------------
12.4XC
------------±----------------------------±-----------------------
12.4XD
------------±----------------------------±-----------------------
12.4XE
------------±----------------------------±-----------------------
12.4XF
------------±----------------------------±-----------------------
12.4XG
------------±----------------------------±-----------------------
12.4XJ
------------±----------------------------±-----------------------
12.4XK
------------±----------------------------±-----------------------
12.4XL
------------±----------------------------±-----------------------
12.4XM
------------±----------------------------±-----------------------
12.4XN
------------±----------------------------±-----------------------
12.4XP
------------±----------------------------±-----------------------
12.4XQ
------------±----------------------------±-----------------------
12.4XR
------------±----------------------------±-----------------------
12.4XT
------------±----------------------------±-----------------------
12.4XV
------------±----------------------------±-----------------------
12.4XW
------------±----------------------------±-----------------------
12.4XY
------------±----------------------------±-----------------------
12.4XZ
------------±----------------------------±-----------------------
12.4YA
------------±----------------------------±-----------------------
12.4YB
------------±----------------------------±-----------------------
12.4YD
±------------------------------------------------------------------+

Workarounds

The following mitigations have been identified for this
vulnerability, which may help protect an infrastructure until an
upgrade to a fixed version of Cisco IOS software can be scheduled:

Infrastructure Access Control Lists
±---------------------------------

Although it is often difficult to block traffic that transits a
network, it is possible to identify traffic that should never be
allowed to target infrastructure devices and block that traffic at
the border of networks. Infrastructure Access Control Lists (iACLs)
are a network security best practice and should be considered as a
long-term addition to good network security as well as a workaround
for these specific vulnerabilities. The iACL example below should be
included as part of the deployed infrastructure access-list which
will protect all devices with IP addresses in the infrastructure IP
address range:

!---
!--- Only sections pertaining to features enabled on the device
!--- need be configured.
!---
!--- Feature: ALPS
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
    INFRASTRUCTURE_ADDRESSES WILDCARD eq 350
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
    INFRASTRUCTURE_ADDRESSES WILDCARD eq 10000

!---
!--- Deny ALPS TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 350
access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 10000

!---
!--- Feature: STUN
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1994
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1990 1992

!---
!--- Deny STUN TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
    INFRASTRUCTURE_ADDRESSES WILDCARD eq 1994
access-list 150 deny tcp any
    INFRASTRUCTURE_ADDRESSES WILDCARD range 1990 1992

!---
!--- Feature: BSTUN
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1963
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1976 1979

!---
!--- Deny BSTUN TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1963
access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1976 1979

!---
!--- Feature: NCIA
!---

!---
!--- Leverage the underlying protocols, DLSw, RSRB, etc.
!---

!---
!--- Feature: DLSW
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 2065
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 2067
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1981 1983

!---
!--- Deny DLSW TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 2065
access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 2067
access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1981 1983

!---
!--- Feature: RSRB
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1987 1989
access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1996

!---
!--- Deny RSRB TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD range 1987 1989
access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1996

!---
!--- Feature: PPTP
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1723

!---
!--- Deny PPTP TCP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1723

!---
!--- Feature: RBP
!---
!--- RBP will listen for TCP connections on the configured port
!--- as per "local port <port_number>". The following example
!--- uses port 1055
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1055

!---
!--- Deny RBP traffic from all other sources destined
!--- to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1055

!---
!--- Feature: XOT and X.25 Routing
!---

access-list 150 permit tcp TRUSTED_HOSTS WILDCARD
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1998

!---
!--- Deny XOT and X25 TCP traffic from all other sources 
!--- destined to infrastructure addresses.
!---

access-list 150 deny tcp any
     INFRASTRUCTURE_ADDRESSES WILDCARD eq 1998

!---
!--- Permit/deny all other Layer 3 and Layer 4 traffic in 
!--- accordance with existing security policies and 
!--- configurations Permit all other traffic to transit the
!--- device.
!---

access-list 150 permit ip any any

!---
!--- Apply access-list to all interfaces (only one example
!--- shown)
!---

interface serial 2/0
 ip access-group 150 in

The white paper entitled "Protecting Your Core: Infrastructure
Protection Access Control Lists" presents guidelines and recommended
deployment techniques for infrastructure protection access lists.
This white paper can be obtained at the following link:
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml

Receive ACLs (rACL)
±-----------------

For distributed platforms, Receive ACLs may be an option starting in
Cisco IOS Software Versions 12.0(21)S2 for the 12000 (GSR), 12.0(24)S
for the 7500, and 12.0(31)S for the 10720. The Receive ACL protects
the device from harmful traffic before the traffic can impact the
route processor. Receive ACLs are designed to only protect the device
on which it is configured. On the 12000, 7500, and 10720, transit
traffic is never affected by a receive ACL. Because of this, the
destination IP address "any" used in the example ACL entries below
only refer to the router's own physical or virtual IP addresses.
Receive ACLs are considered a network security best practice, and
should be considered as a long-term addition to good network
security, as well as a workaround for this specific vulnerability.
The white paper entitled "Protecting Your Core: Infrastructure
Protection Access Control Lists" presents guidelines and recommended
deployment techniques for infrastructure protection access lists.
This white paper can be obtained at the following link
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a0a5e.shtml

The following is the receive path ACL written to permit this type of
traffic from trusted hosts:

!---
!--- Only sections pertaining to features enabled on the device
!--- need be configured.
!---

!---
!--- Permit ALPS traffic from trusted hosts allowed to the RP.
!--- 

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 350
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
    any eq 10000

!---
!--- Deny ALPS traffic from all other sources to the RP.
!--- 

access-list 150 deny tcp any any eq 350
access-list 150 deny tcp any any eq 10000

!---
!--- Permit STUN traffic from trusted hosts allowed to the RP.
!--- 

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1994
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any range 1990 1992

!---
!--- Deny STUN traffic from all other sources to the RP.
!--- 

access-list 150 deny tcp any any eq 1994
access-list 150 deny tcp any any eq range 1990 1992

!---
!--- Permit BSTUN traffic from trusted hosts allowed to the RP.
!--- 

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1963
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any range 1976 1979

!---
!--- Deny BSTUN traffic from all other sources to the RP.
!--- 

access-list 150 deny tcp any any eq 1963
access-list 150 deny tcp any any eq range 1976 1979

!---
!--- Permit DLSw from trusted hosts allowed to the RP.
!--- 

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 2065
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 2067
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any range 1981 1983

!---
!--- Deny DLSw all other sources to the RP.
!--- 

access-list 150 deny tcp any any eq 2065
access-list 150 deny tcp any any eq 2067
access-list 150 deny tcp any any range 1981 1983

!---
!--- Permit RSRB traffic from trusted hosts allowed to the RP.
!---

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1996
access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any range 1987 1989

!---
!--- Deny RSRB traffic from all other sources to the RP.
!---

access-list 150 deny tcp any any eq 1996
access-list 150 deny tcp any any range 1987 1989

!--- 
!--- Permit PPTP traffic from trusted hosts allowed to the RP.
!--- 

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1723

!---
!--- Deny PPTP traffic from all other sources to the RP.
!--- 

access-list 150 deny tcp any any eq 1723

!---
!--- Permit RBP traffic from trusted hosts allowed to the RP.
!--- RBP will listen for TCP connections on the configured port
!--- as per "local port <port_number>".  The following example
!--- uses port 1055
!---

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1055

!---
!--- Deny RBP traffic from all other sources to the RP.
!---

access-list 150 deny tcp any any eq 1055

!---
!--- Permit XOT and X.25 Routing traffic from trusted hosts allowed 
!--- to the RP.
!---

access-list 150 permit tcp TRUSTED_SOURCE_ADDRESSES WILDCARD
     any eq 1998

!---
!--- Deny XOT and X.25 Routing traffic from all other sources to 
!---  the RP.
!---

access-list 150 deny tcp any any  eq 1998

!--- Permit all other traffic to the RP.
!--- according to security policy and configurations.

access-list 150 permit ip any any

!--- Apply this access list to the 'receive' path.

ip receive access-list 150

Control Plane Policing
±--------------------

Control Plane Policing (CoPP) can be used to block the affected
features TCP traffic access to the device. Cisco IOS software
releases 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T support the
CoPP feature. CoPP can be configured on a device to protect the
management and control planes and minimize the risk and effectiveness
of direct infrastructure attacks by explicitly permitting only
authorized traffic that is sent to infrastructure devices in
accordance with existing security policies and configurations. The
CoPP example below should be included as part of the deployed CoPP
that will protect all devices with IP addresses in the infrastructure
IP address range.

!---
!--- Only sections pertaining to features enabled on the device
!--- need be configured.
!---
!--- Feature: ALPS
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD any eq 350
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD any eq 10000

!---
!--- Permit ALPS traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 350
access-list 150 permit tcp any any eq 10000

!---
!--- Feature: STUN
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1994
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any range 1990 1992

!---
!--- Permit STUN traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 1994
access-list 150 permit tcp any any range 1990 1992

!---
!--- Feature: BSTUN
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1963
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any range 1976 1979

!---
!--- Permit BSTUN traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 1963
access-list 150 permit tcp any any range 1976 1979

!---
!--- Feature: NCIA
!---
!--- Leverage the underlying protocols, DLSw, RSRB, etc.
!---

!---
!--- Feature: DLSW
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 2065
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 2067
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any range 1981 1983

!---
!--- Permit DLSW traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 2065
access-list 150 permit tcp any any eq 2067
access-list 150 permit tcp any any range 1981 1983

!---
!--- Feature: RSRB
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any range 1987 1989
access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1996

!---
!--- Permit RSRB traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any range 1987 1989
access-list 150 permit tcp any any eq 1996

!---
!--- Feature: PPTP
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1723

!---
!--- Permit PPTP traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 1723

!---
!--- Feature: RBP
!---
!--- RBP will listen for TCP connections on the configured port
!--- as per "local port <port_number>".  The following example
!--- uses port 1055

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1055

!---
!--- Permit RBP traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 1055

!---
!--- Feature: XOT and X.25 Routing
!---

access-list 150 deny tcp TRUSTED_HOSTS WILDCARD
     any eq 1998

!---
!--- Permit XOT and X25 traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so 
!--- that it will be policed and dropped by the CoPP feature
!---

access-list 150 permit tcp any any eq 1998

!---
!--- Permit (Police or Drop)/Deny (Allow) all other Layer3 and 
!--- Layer4 traffic in accordance with existing security policies
!--- configurations for traffic that is authorized to be sent
!--- and to infrastructure devices
!--- Create a Class-Map for traffic to be policed by
!--- the CoPP feature
!---

class-map match-all drop-tcp-class
 match access-group 150

!---
!--- Create a Policy-Map that will be applied to the
!--- Control-Plane of the device.
!---

policy-map drop-tcp-traffic
 class drop-tcp-class
  drop

!---
!--- Apply the Policy-Map to the 
!--- Control-Plane of the device
!---

control-plane
 service-policy input drop-tcp-traffic

In the above CoPP example, the access control list entries (ACEs)
that match the potential exploit packets with the "permit" action
result in these packets being discarded by the policy-map "drop"
function, while packets that match the "deny" action (not shown) are
not affected by the policy-map drop function. Please note that the
policy-map syntax is different in the 12.2S and 12.0S Cisco IOS
trains:

policy-map drop-tcp-traffic
  class drop-tcp-class
    police 32000 1500 1500 conform-action drop exceed-action drop

Additional information on the configuration and use of the CoPP
feature can be found in the documents, "Control Plane Policing
Implementation Best Practices" and "Cisco IOS Software Releases 12.2S

Additional mitigations that can be deployed on Cisco devices within
the network are available in the "Cisco Applied Mitigation Bulletin"
companion document for this advisory, at the following link
http://www.cisco.com/warp/public/707/cisco-amb-20090325-tcp-and-ip.shtml

Obtaining Fixed Software

Cisco has released free software updates that address these
vulnerabilities. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets
they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound
by the terms of Cisco's software license terms found at
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml

Do not contact [email protected] or [email protected] for
software upgrades.

Customers with Service Contracts
±------------------------------

Customers with contracts should obtain upgraded software through
their regular update channels. For most customers, this means that
upgrades should be obtained through the Software Center on Cisco's
worldwide website at http://www.cisco.com

Customers using Third Party Support Organizations
±-----------------------------------------------

Customers whose Cisco products are provided or maintained through
prior or existing agreements with third-party support organizations,
such as Cisco Partners, authorized resellers, or service providers
should contact that support organization for guidance and assistance
with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.

Customers without Service Contracts
±---------------------------------

Customers who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party
vendors but are unsuccessful in obtaining fixed software through
their point of sale should acquire upgrades by contacting the Cisco
Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: [email protected]

Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to
a free upgrade. Free upgrades for non-contract customers must be
requested through the TAC.

Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
for additional TAC contact information, including localized telephone
numbers, and instructions and e-mail addresses for use in various
languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.

This vulnerability was found by Cisco internal testing.

Status of this Notice: FINAL

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.

Distribution

This advisory is posted on Cisco's worldwide website at :

http://www.cisco.com/warp/public/707/cisco-sa-20090325-tcp.shtml

In addition to worldwide web posting, a text version of this notice
is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the above URL for any updates.

Revision History

±--------------------------------------+
| Revision | | Initial |
| 1.0 | 2009-March-25 | public |
| | | release |
±--------------------------------------+

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html
This includes instructions for press inquiries regarding Cisco
security notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt
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