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Blue Coat WinProxy Remote DoS Vulnerability

01.05.06

BACKGROUND

BlueCoat WinProxy is an Internet sharing proxy server designed for small
to medium businesses. In addition to Internet sharing Winproxy also
hosts a series of security, anti-spam and anti-spyware capabilities.

More information can be located from the vendors site at:

  http://www.winproxy.com/

DESCRIPTION

Remote exploitation of a design error in Blue Coat Systems Inc.'s
WinProxy allows attackers to cause a denial of service (DoS) condition.

The vulnerability specifically exists due to improper handling of a long
HTTP request that is approximately 32,768 bytes long. When such a
request occurs, the process will crash while attempting to read past the
end of a memory region.

ANALYSIS

Successful exploitation requires an attacker to send a specially
constructed HTTP request to the WinProxy server on TCP port 80. This
will lead to a crash of the server and it will be unusable until it is
restarted.

This vulnerability may only be utilized by attackers who have access to
the network segment that contains the listening daemon, which in some
cases is a private local area network.

DETECTION

iDefense has confirmed this vulnerability in WinProxy 6.0. Blue Coat has
reported that previous versions are not affected.

WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

VENDOR RESPONSE

Blue Coat has released WinProxy 6.1a to address this vulnerability.

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-3187 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

10/12/2005   Initial vendor notification
10/12/2005   Initial vendor response
01/05/2006   Coordinated public disclosure

CREDIT

FistFuXXer is credited with the discovery of this vulnerability.

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LEGAL NOTICES

Copyright © 2006 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.