MS-ISAC ADVISORY NUMBER:
2009-005

DATE(S) ISSUED:
2/10/2009

SUBJECT:
Vulnerabilities in Internet Explorer Could Allow Remote Code Execution

OVERVIEW:

Two vulnerabilities have been discovered in Microsoft's browser, Internet Explorer, which could allow an attacker to take complete control of an affected system. Exploitation may occur if a user visits a web page which is specifically crafted to take advantage of these announced vulnerabilities. Successful exploitation 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.

SYSTEMS AFFECTED:

  • Internet Explorer 7
  • Internet Explorer 8 Beta

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

DESCRIPTION:
Two vulnerabilities have been discovered in Microsoft Internet Explorer that could allow an attacker to take complete control of an affected system. Details of these vulnerabilities are as follows:

Unitialized Memory Corruption Vulnerability
A remote code vulnerability has been discovered in the way Internet Explorer accesses memory. This vulnerability is caused by Internet Explorer attempting to access uninitialized or deallocated memory.

CSS Memory Corruption Vulnerability
A remote code vulnerability has been discovered in the way Internet Explorer handles Cascading Style Sheets (CSS). CSS is a stylesheet language used to define the presentation of a document written in HTML, XML, or similar markup language. The vulnerability is caused by Internet Explorer improperly processing certain CSS styles, resulting in memory corruption.

Both of these vulnerabilities can be exploited by an attacker if a user visits a specially crafted malicious web site. Successful exploitation could allow an attacker to execute arbitrary code on the affected system. Depending on the privileges associated with the user, the attacker could then install programs; view, change, or delete data; or create new accounts with full privileges.

RECOMMENDATIONS:
We recommend the following actions be taken:

  • Apply appropriate patches provided by Microsoft to vulnerable systems immediately after appropriate testing.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Do not visit un-trusted websites or follow links provided by unknown or un-trusted sources.

REFERENCES:
Microsoft:
http://www.microsoft.com/technet/security/Bulletin/MS09-002.mspx(New Window)

Security Focus:
http://www.securityfocus.com/bid/33627(New Window)
http://www.securityfocus.com/bid/33628(New Window)

CVE:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0075(New Window)
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0076(New Window)

This cyber advisory was issued by the Multi-State Information Sharing and Analysis Center (MS-ISAC) and was intended for government entities. The information may or may not be applicable to the general public and accordingly, the MS-ISAC does not warrant its use for any specific purposes.