OCS ADVISORY NUMBER:
2010-097 - Updated

DATE(S) ISSUED:
11/3/2010
11/4/2010 - UPDATED
12/14/2010 - UPDATED

SUBJECT:
Vulnerability in Internet Explorer Could Allow Remote Code Execution

ORIGINAL OVERVIEW:

A vulnerability has been discovered in Microsoft's web browser, Internet Explorer, which could allow an attacker to take complete control of an affected system. Exploitation may occur if a user visits or is redirected to a web page which is specifically crafted to take advantage of the vulnerability. Successful exploitation of this vulnerability could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

It should be noted that there is no patch available at this time andThere are reports that it is being exploited for targeted attacks.

November 4 - UPDATED OVERVIEW:
Proof-of-concept code has been made publically available for this vulnerability.

A patch is still not available, however Microsoft has released a Fix it solution that automates the work around process of enabling DEP for IE 7 and is discussed in the 'Frequently Asked Question' section of the Microsoft advisory. Please see the Microsoft advisory in references for additional information.

December 14 - UPDATED OVERVIEW:
A patch has been made available for this vulnerability.

SYSTEMS AFFECTED:

• Internet Explorer 6
• Internet Explorer 7
• Internet Explorer 8

RISK:
Government:

• Large and medium government entities: High
• Small government entities: High

Businesses:

• Large and medium business entities: High
• Small business entities: High

Home users: High
ORIGINAL DESCRIPTION:
A vulnerability has been discovered in Microsoft's web browser, Internet Explorer, which could allow an attacker to take complete control of an affected system.  This vulnerability occurs when a certain combination of Cascading Style Sheet (CSS) tags are stored, which may result in a use-after-free condition. A use-after-free condition is when an application deallocates a memory block and then later attempts to access that deallocated space.

Exploitation may occur if a user visits or is redirected to a web page which is specifically crafted to take advantage of these vulnerabilities. Successful exploitation of the vulnerability could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

It should be noted that there is no patch available at this time andThere are reports that it is being exploited for targeted attacks.

November 4 - UPDATED DESCRIPTION:
Proof-of-concept code has been made publically available for this vulnerability.

A patch is still not available, however Microsoft has released a Fix it solution that automates the work around process of enabling DEP for IE 7 and is discussed in the 'Frequently Asked Question' section of the Microsoft advisory. Please see the Microsoft advisory in references for additional information.

December 14 - UPDATED DESCRIPTION:
Microsoft has released a patch (MS10-090) which addresses this vulnerability.

ORIGINAL RECOMMENDATIONS:
We recommend the following actions be taken:

• Consider implementing the following workarounds as recommended by Microsoft:
• Override the Web site CSS style with a user defined CSS.
• Deploy the Enhanced Mitigation Experience Toolkit.
• Enable Data Execution Prevention for IE 7.
• Read e-mail in plain-text format.
• Set Internet and Local Intranet security zone settings to "high" to block ActiveX controls and Active Scripting.
• Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
• Inform and educate users regarding the threats posed by hypertext links contained in e-mails or attachments especially from un-trusted sources.
• If you have an alternate browser deployed, consider using it until this vulnerability is remediated.

December 14 - UPDATED RECOMMENDATIONS:
We recommend the following actions be taken:

• Apply appropriate patch provided by Microsoft immediately after appropriate testing.

REFERENCES:
Microsoft:
http://www.microsoft.com/technet/security/advisory/2458511.mspx

CVE:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3962

Symantec:
http://www.symantec.com/connect/blogs/new-ie-0-day-used-targeted-attacks

SANS:
http://isc.incidents.org/diary.html?storyid=9874

Security Focus:
http://www.securityfocus.com/bid/44536

December 14 - UPDATED REFERENCES
Microsoft:
http://www.microsoft.com/technet/security/bulletin/ms10-090.mspx