Microsoft Windows VML fails to properly handle compressed content, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.
Microsoft IE version 5.0 and higher supports the Vector Markup Language (VML), which is a set of XML tags for drawing vector graphics. VGX.DLL provides VML support for Internet Explorer. VGX.DLL contains an integer underflow vulnerability in the handling of compressed VML content.
By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), a remote, unauthenticated attacker may be able to execute arbitrary code with the privileges of the user. The attacker could also cause Internet Explorer (or the program using the WebBrowser control) to crash.
Apply an update
This issue is addressed by Microsoft Security Bulletin MS07-050. This bulletin provides an updated version of VGX.DLL.
Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this and other ActiveX vulnerabilities. Instructions for disabling ActiveX in the Internet Zone can be found in the "Securing Your Web Browser" document.
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.
Disable Active Scripting
Although this vulnerability does not require Active Scripting to be enabled, known exploits targeting this issue use Active Scripting to place malicious code on a vulnerable system. To block this attack vector, it is recommended that Active Scripting be disabled. For instructions on how to disable Active Scripting in Microsoft Internet Explorer, please refer to the Internet Explorer section of the Securing Your Web Browser document.
Thanks to Microsoft for reporting this vulnerability, who in turn credit eEye Digital Security.
This document was written by Will Dormann.
|Date First Published:||2007-08-14|
|Date Last Updated:||2007-08-17 12:32 UTC|