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Microsoft Internet Explorer long URL buffer overflow

Vulnerability Note VU#821156

Original Release Date: 2006-08-22 | Last Revised: 2006-08-24


Microsoft Internet Explorer is vulnerable to a buffer overflow when processing a long URL on a web site that uses HTTP 1.1 compression. This could allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.


Microsoft Internet Explorer 6 Service Pack 1 on Windows 2000 and Windows XP SP1 contains a vulnerability when viewing a web site using the HTTP 1.1 protocol. If the web site uses HTTP 1.1 compression and contains an overly long URL, a buffer overflow can occur.

Note that this vulnerability was introduced with the first release of the MS06-042 updates on August 8, 2006.


By convincing a user to view a specially crafted HTML document (e.g., a web page, an HTML email message, or an email attachment), an attacker could execute arbitrary code with the privileges of the user. The attacker could also cause Internet Explorer (or the program using the WebBrowser ActiveX control) to crash.


Apply an update
This vulnerability is addressed in Microsoft Security Bulletin MS06-042 version 2.0.

Disable Active Scripting

This vulnerability can be mitigated by disabling Active Scripting, as specified in the "Securing Your Web Browser" document. While this does not remove the vulnerability, it does block known techniques to exploit this vulnerability to execute arbitrary code.

Disable HTTP 1.1

This vulnerability can be mitigated by disabling HTTP 1.1, as specified in Microsoft Security Advisory 923762.

Vendor Information


Microsoft Corporation Affected

Notified:  August 21, 2006 Updated: August 24, 2006



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


Please see Microsoft Security Bulletin MS06-042.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

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Thanks to Dejan Kovacevic of Bold Internet Solutions for reporting this vulnerability.

This document was written by Will Dormann.

Other Information

CVE IDs: CVE-2006-3869
Severity Metric: 13.37
Date Public: 2006-08-22
Date First Published: 2006-08-22
Date Last Updated: 2006-08-24 18:12 UTC
Document Revision: 13

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