IE 8/9 mshtml.dll NULL_IMPORT_DESCRIPTOR Use After Free

Date Disclosed:
9/17/2013

Date Patched:
Patch Not Yet Available

Vendor:
Microsoft
Affected Software:
Internet Explorer 6
Internet Explorer 7
Internet Explorer 8 (in the wild, targeted attacks focusing on XP and 7)
Internet Explorer 9 (in the wild, targeted attacks focusing on XP and 7)
Internet Explorer 10
Internet Explorer 11


Description:

There is a use after free in Internet Explorer, that when combined with a non-ASLR Office DLL, can allow for remote code execution in the context of the currently logged on user. This attack has been spotted in the wild in Japan, in targeted attacks. The attack is not widespread yet. However, with the introduction of a Microsoft Fix it, attackers may be able to more easily deduce the vulnerability being targeted, and produce exploits.
Severity:
High
Code Execution:
Yes.
Impact:
Remote Code Execution
Exploitation of this vulnerability is possible through the use of methods like drive-by attacks. Remote attackers who successfully exploit this vulnerability will be able to execute code on the vulnerable system with the same rights as the currently logged on user.
Mitigation:
Apply the Microsoft Fix it immediately to prevent exploitation. Additionally, EMET 4.0 mitigates this attack. Otherwise, use other browsers such as Chrome.
Protection:
BeyondTrust's Retina® Network Security Scanner scans devices to detect for this vulnerability.

• 30541 - Microsoft Internet Explorer MSHTML NULL_IMPORT_DESCRIPTOR (Zero-Day)
• 30542 - Microsoft Internet Explorer MSHTML NULL_IMPORT_DESCRIPTOR (Zero-Day) - x64

Links:

• Microsoft Fix it
• Microsoft Advisory
• Microsoft TechNet Blog

Status:
2013-09-17 - Public advisory released