NY.gov Portal State Agency Listing
The following cyber advisory was issued by the New York State Office of Information Technology Services and is intended for State government entities. The information may or may not be applicable to the general public and, accordingly, the State does not warrant its use for any specific purposes.

ITS ADVISORY NUMBER:
2010-108 Updated

DATE(S) ISSUED:
12/21/2010
1/11/2011 - 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. Failed exploit attempts may result in a denial-of-service condition.

It should be noted that there is currently no patch available for this vulnerability and a working exploit is available which results in remote code execution.  The exploit has been tested with Internet Explorer 7 & 8 on a Windows XP SP3 platform and confirmed to result in remote code execution.

January 11, 2011 - UPDATED OVERVIEW:
Microsoft has released a workaround for this vulnerability. It should be noted that you must first install all previous security updates including the security update addressed in MS10-090. All information regarding this workaround can be found here: http://support.microsoft.com/kb/2488013

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 rendering a web page containing a reference to a Cascading Style Sheet (CSS) file with "@import" rules. This may result in a use-after-free condition in the mshtml.dll library. A use-after-free condition occurs when an application de-allocates a memory block and then later attempts to access that de-allocated 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. Failed exploit attempts may result in a denial-of-service condition.

It should be noted that there is currently no patch available for this vulnerability and a working exploit is available which results in remote code execution.  The exploit has been tested with Internet Explorer 7 & 8 on a Windows XP SP3 platform and confirmed to result in remote code execution.

January 11, 2011 - UPDATED DESCRIPTION:
Microsoft has released a workaround for this vulnerability. It should be noted that you must first install all previous security updates including the security update addressed in MS10-090. This workaround enables Internet Explorer to refuse to import a CSS style sheet if it has the same URL as the CSS style sheet from which it is being loaded. All further information regarding this workaround can be found here: http://support.microsoft.com/kb/2488013

ORIGINAL RECOMMENDATIONS: 
We recommend the following actions be taken:

  • Set Internet and Local Intranet security zone settings 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.
  • Read e-mail in plain-text format.
  • Inform and educate users regarding the threats posed by hypertext links contained in e-mails or attachments especially from untrusted sources.
  • If you have an alternate browser deployed, consider using it until this vulnerability is remediated.

January 11, 2011 - UPDATED RECOMMENDATIONS:
We recommend the following actions be taken:

ORIGINAL REFERENCES:
US-CERT: 
http://www.kb.cert.org/vuls/id/634956

Secunia:
http://secunia.com/advisories/42510

Threat Post: 
http://threatpost.com/en_us/blogs/new-remotely-exploitable-bug-found-internet-explorer-121010

Security Focus:
http://www.securityfocus.com/bid/45246

Metasploit:
https://www.metasploit.com/redmine/projects/framework/repository/entry/modules/exploits/windows/browser/ms11_xxx_ie_css_import.rb

January 11, 2011 - UPDATED REFERENCES:
Microsoft:
http://www.microsoft.com/technet/security/advisory/2488013.mspx
http://support.microsoft.com/kb/2488013
http://blogs.technet.com/b/srd/archive/2011/01/11/new-workaround-included-in-security-advisory-2488013.aspx
http://download.microsoft.com/download/E/5/6/E56904FD-3370-479D-B14A-E5481222C59C/MicrosoftFixit50591.msi- Workaround
http://www.microsoft.com/technet/security/bulletin/MS10-090.mspx