US-CERT Technical Cyber Security Alert TA08-297A -- Microsoft Windows Server Service RPC Vulnerability

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                 National Cyber Alert System

           Technical Cyber Security Alert TA08-297A

Microsoft Windows Server Service RPC Vulnerability

Original release date: October 23, 2008
Last revised: –
Source: US-CERT

Systems Affected

 * Microsoft Windows 2000
 * Microsoft Windows XP
 * Microsoft Windows Server 2003
 * Microsoft Windows Vista
 * Microsoft Windows Server 2008

Overview

A vulnerability in the way the Microsoft Windows server service
handles RPC requests could allow an unauthenticated, remote
attacker to execute arbitrary code with SYSTEM privileges.

I. Description

Microsoft has released Microsoft Security Bulletin MS08-067 to
address a buffer oveflow vulnerability in the Windows Server
service. The vulnerability is caused by a flaw in the way the
Server service handles Remote Procedure Call (RPC) requests. For
systems running Windows 2000, XP, and Server 2003, a remote,
unauthenticated attacker could exploit this vulnerability. For
systems running Windows Vista and Server 2008, a remote attacker
would most likely need to authenticate.

Microsoft Security Bulletin MS08-067 rates this vulnerability as
"Critical" for Windows 2000, XP, and Server 2003. The bulletin also
notes "…limited, targeted attacks attempting to exploit the
vulnerability."

This vulnerability has been assigned CVE-2008-4250. Further
information is available in a Security Vulnerability & Research
blog entry and US-CERT Vulnerability Note VU#827267.

II. Impact

A remote, unauthenticated attacker could execute arbitrary code or
cause a vulnerable system to crash. Since the Server service runs
with SYSTEM privileges, an attacker could take complete control of
a vulnerable system.

III. Solution

Apply update

Microsoft has provided updates for this vulnerability in Microsoft
Security Bulletin MS08-067. Microsoft also provides security
updates through the Microsoft Update web site and Automatic
Updates. System administrators should consider using an automated
update distribution system such as Windows Server Update Services
(WSUS).

Disable Server and Computer Browser services

Disable the Server and Computer Browser services on Windows systems
that do not require those services. A typical Windows client that
is not sharing files or printers is unlikely to need either the
Server or Computer Browser services. As a best security practice,
disable all unnecessary services.

Restrict access to server service

Restrict access to the server service (TCP ports 139 and 445). As a
best security practice, only allow access to necessary network
services.

Filter affected RPC identifier

The host firewalls in Windows Vista and Windows Server 2008 can
selectively filter RPC Universally Unique Identifiers (UUID). See
Microsoft Security Bulletin MS08-067 for instructions to filter RPC
requests with the UUID equal to
4b324fc8-1670-01d3-1278-5a47bf6ee188.

IV. References

 * US-CERT Vulnerability Note VU#827267 -
   <http://www.kb.cert.org/vuls/id/827267>

 * Microsoft Security Bulletin MS08-067 -
   <http://www.microsoft.com/technet/security/Bulletin/
   ms08-067.mspx>

 * Microsoft Update - <https://update.microsoft.com/>

 * Windows Update: Automatic Update
   <http://www.microsoft.com/windows/downloads/windowsupdate/
   automaticupdate.mspx>

 * Windows Server Update Services (WSUS) Home -
   <http://technet.microsoft.com/en-us/wsus/default.aspx>

 * CVE-2008-4250 -
   <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4250>

 * More detail about MS08-067, the out-of-band netapi32.dll
   security update -
   <http://blogs.technet.com/swi/archive/2008/10/23/
   More-detail-about-MS08-067.aspx>

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The most recent version of this document can be found at:

 <http://www.us-cert.gov/cas/techalerts/TA08-297A.html>

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Feedback can be directed to US-CERT Technical Staff. Please send
email to <[email protected]> with "TA08-297A Feedback VU#827267" in
the subject.

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Produced 2008 by US-CERT, a government organization.

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Revision History

October 23, 2008: Initial release

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