Vulnerability Note VU#136849

Microsoft Internet Explorer UTF-8 decoding vulnerability

The Unicode character set contains more than 96,000 characters. Because of this, Unicode can be used to represent a wide range of languages.

UTF-8

UTF-8 (Unicode Tranlation Format 8) is a type of character encoding for Unicode character sets.

The problem

Internet Explorer fails to properly calculate memory sizes when decoding UTF-8 encoded characters. This can cause heap memory corruption.

II. Impact

This issue is addressed in Microsoft Security Bulletin MS06-021. This update modifies the way that Internet Explorer decodes UTF-8 encoded HTML.

Read and send email in plain text format

Outlook 2003, Outlook 2002 SP1, and Outlook 6 SP1 can be configured to view email messages in text format. Consider the security of fellow Internet users and send email in plain text format when possible.

Do not follow unsolicited links

In order to convince users to visit their sites, attackers often use URL encoding, IP address variations, long URLs, intentional misspellings, and other techniques to create misleading links. Do not click on unsolicited links received in email, instant messages, web forums, or internet relay chat (IRC) channels. Type URLs directly into the browser to avoid these misleading links. While these are generally good security practices, following these behaviors will not prevent exploitation of this vulnerability in all cases, particularly if a trusted site has been compromised or allows cross-site scripting.

Systems Affected

http://www.microsoft.com/technet/security/Bulletin/MS06-021.mspx
http://www.zerodayinitiative.com/advisories/ZDI-06-017.html

Credit

Thanks to Microsoft Security for reporting this vulnerability. Microsoft, in turn, thanks Tippingpoint for reporting this issue.

This document was written by Will Dormann.

Other Information

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