Web Request Can Cause Access Violation in ISA Server Web Proxy Service New

A security vulnerability exists in Microsoft ISA Server 2000 which could allow a remote attackers to cause a denial of service resulting in the failure of the Web Proxy service.

Issue

The ISA Server Web Proxy service does not correctly handle a certain type of web request if it exceeds a particular length. Processing such a request would result in an access violation, which would cause the Web Proxy service to fail. This would disrupt all ingoing and outgoing web proxy requests until the service was restarted.

Under most conditions, a user on the Internet could not exploit the vulnerability, as ISA Server will ignore external requests unless the Web Publishing feature is enabled. However, if an external attacker were able to persuade an internal user to visit a web page or open an HTML e-mail, it could be possible to embed an URL that would exploit the vulnerability from within the network.

Affected Products

• Microsoft ISA Server 2000

Download

Patch: http://a1060.ms.a.microsoft.com/f/1060/1611/2h/download.microsoft.com/download/ISAServer2000/webproxy/Q295279/NT5/EN-US/isahf63.exe

Further Details

Source: Microsoft Corporation

Reference: Microsoft Corporation

Updated: April 17, 2001

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