Vulnerability in Microsoft Internet Explorer

Systems Affected

• Internet Explorer versions 6.0 and later

Overview

By taking advantage of a vulnerability in Internet Explorer, an attacker may be able to take control of your computer.

Solution

Apply an update

Microsoft has released an update to resolve this problem. Obtain the appropriate update from Windows Update or by using Automatic Updates.

Upgrade to Windows XP SP2

Windows XP Service Pack 2 is not affected. If you are running Windows XP, you can install Service Pack 2 using Windows Update or Automatic Updates.

Follow good security practices

The following practices may offer additional protection against this vulnerability:

• Disable Active scripting - Attackers may be able to take advantage of Active scripting to exploit this vulnerability. Instructions for disabling Active scripting are available in the Malicious Web Scripts FAQ.

• Don't follow unsolicited links - By convincing you to follow a link, an attacker may be able to send you to a malicious site. Don't click on unsolicited URLs received in email, instant messages, web forums, or Internet relay chat (IRC) channels.

• Read and send email in plain text format - Many email clients use the same programs as web browsers to display HTML, so vulnerabilities that affect active content like JavaScript and ActiveX often apply to email.

• Maintain updated anti-virus software - It is important that you use anti-virus software and keep it up to date. Most anti-virus software vendors frequently release updated information, tools, or virus databases to help detect and recover from virus infections. Many anti-virus packages support automatic updates of virus definitions. US-CERT recommends using these automatic updates when possible.

Description

There is a vulnerability in the way Internet Explorer processes certain HTML code. By exploiting the vulnerability, an attacker may be able to take control of your computer or cause a denial of service.

For more technical information, see TA04-315A.

References

• Windows Security Update for December 2004 - <http://www.microsoft.com/security/bulletins/200412_windows.mspx>
• Browsing Safely: Understanding Active Content and Cookies - <http://www.us-cert.gov/cas/tips/ST04-012.html>
• Understanding Anti-Virus Software - <http://www.us-cert.gov/cas/tips/ST04-005.html>
• Understanding Denial-of-Service Attacks - <http://www.us-cert.gov/cas/tips/ST04-015.html>
• Security Improvements in Windows XP Service Pack 2 - <http://www.us-cert.gov/cas/alerts/SA04-243A.html>
• US-CERT Technical Cyber Security Alert TA04-315A - <http://www.us-cert.gov/cas/techalerts/TA04-315A.html>
• US-CERT Technical Cyber Security Alert TA04-336A - <http://www.us-cert.gov/cas/techalerts/TA04-336A.html>
• Vulnerability Note VU#842160 - <http://www.kb.cert.org/vuls/id/842160>

Feedback can be directed to US-CERT.

Copyright 2004 Carnegie Mellon University. Terms of use

Revision History

November 10, 2004: Initial release
December 3, 2004: Added information about MS04-040 update, SA04-336A, and TA04-336A, updated Systems Affected