-----BEGIN PGP SIGNED MESSAGE-----

---

Title: Flaw In Winsock Proxy Service And ISA Firewall Service
Can Cause Denial Of Service (331066)
Date: 09 April 2003
Software: Microsoft Proxy Server 2.0, Microsoft ISA Server
Impact: denial of service
Max Risk: Important
Bulletin: MS03-012

Microsoft encourages customers to review the Security Bulletins
at:

http://www.microsoft.com/technet/security/bulletin/MS03-012.asp
http://www.microsoft.com/security/security_bulletins/ms03-012.asp

---

Issue:

There is a flaw in the Winsock Proxy service in Microsoft Proxy
Server 2.0, and the Microsoft Firewall service in ISA Server 2000,
that would allow an attacker on the internal network to send a
specially crafted packet that would cause the server to stop
responding to internal and external requests. Receipt of such a
packet would cause CPU utilization on the server to reach 100%, and
thus make the server unresponsive. The Winsock Proxy service and
Microsoft Firewall service work with FTP, telnet, mail, news,
Internet Relay Chat (IRC), or other client applications that are
compatible with Windows Sockets (Winsock). These services allow
these applications to perform as if they were directly connected to
the Internet. These services redirect the necessary communications
functions to a Proxy Server 2.0 or ISA Server computer, thus
establishing a communication path from the internal application to
the Internet through it.

Mitigating Factors:

• • The vulnerability would not enable an attacker to gain any
    privileges on an affected Proxy Server 2.0 or ISA Server computer
    or compromise any cached content. It is strictly a denial of
    service.
• • ISA Server computers running in cache mode are not affected
    because the Microsoft Firewall service is disabled by default.

Risk Rating:

Important

Patch Availability:

A patch is available to fix this vulnerability. Please read the
Security Bulletins at

http://www.microsoft.com/technet/security/bulletin/ms03-012.asp
http://www.microsoft.com/security/security_bulletins/ms03-12.asp

for information on obtaining this patch.

---

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT
DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING
THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS
SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT,
INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR
SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS
HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME
STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR
CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION
MAY NOT APPLY.

-----BEGIN PGP SIGNATURE-----
Version: PGP 7.1

iQEVAwUBPpRVY40ZSRQxA/UrAQG2pQf/Ul+QJaTR+qnbNvyp9Z9ypv2MS1ryDe6J
g+S1HMmVFGgs5T5k7I4xQBc7KjWsr6Hm7wVabItomQVyR7fc7pI9a1fNFkewyVw+
yHFIoOGaee3/vQ3eFRhEN8zPGXswgHB6Th3BWfk1qK51XxDQusywGXjzDRNRJlCb
hJbjs/HXt6Z+WqtbHE1uuoH92/+BgCIBqptIXgHcWRC7jzRGZNNoj8Z2vmw9EcWc
9xjtvlnGVNyy14GYwZvNevD3JoVLZ4AjCDvJj+D6d1nHHW3IXY12Pj3gyjIXWNhu
gvv6U6eTPBKCNO7/XkeAfy8e7tC2lkmVPvCYiIbIQVHxu3/aSYry5A==
=zsNm
-----END PGP SIGNATURE-----

---

You have received this e-mail bulletin because of your subscription to the Microsoft Product Security
Notification Service. For more information on this service, please visit
http://www.microsoft.com/technet/security/notify.asp.

To verify the digital signature on this bulletin, please download our PGP key at
http://www.microsoft.com/technet/security/notify.asp.

To unsubscribe from the Microsoft Security Notification Service, please visit the Microsoft Profile
Center at http://register.microsoft.com/regsys/pic.asp

If you do not wish to use Microsoft Passport, you can unsubscribe from the Microsoft Security
Notification Service via email as described below:
Reply to this message with the word UNSUBSCRIBE in the Subject line.

For security-related information about Microsoft products, please visit the Microsoft Security Advisor
web site at http://www.microsoft.com/security.