Vulnerability Note VU#744549

Microsoft Internet Explorer iepeers.dll use-after-free vulnerability

Overview

Microsoft Internet Explorer contains a use-after-free vulnerability in the iepeers.dll file, which may allow a remote, unauthenticated attacker to execute arbitrary code.

I. Description

Microsoft Internet Explorer provides support for Web Folders and printing through the use of the iepeers.dll component. According to Microsoft Security Advisory (981374), the iepeers.dll contains a vulnerability in the use of a pointer after an object is freed. Microsoft reports that the vulnerability, which affects Internet Explorer 6 and 7, has been reported publicly.

Exploit code for this vulnerability is publicly available. This vulnerability is currently being exploited in the wild.

II. Impact

By convincing a user to load a specially crafted HTML document or Microsoft Office document, a remote, unauthenticated attacker may be able to execute arbitrary code or cause a denial-of-service condition.

III. Solution

Apply an update

This issue is addressed in Microsoft Security Bulletin MS10-018, which modifies the way Internet Explorer handles objects in memory.

Enable Data Execution Prevention (DEP) on Internet Explorer 6 or Internet Explorer 7

Microsoft has published more information on DEP as a mitigation for this vulnerability. DEP should not be treated as a complete workaround, but DEP can mitigate the execution of attacker-supplied code in some cases. Microsoft has published detailed technical information about DEP in Security Research & Defense blog posts "Understanding DEP as a mitigation technology" part 1 and part 2. Use of DEP should be considered in conjunction with other mitigations described in this document.

Set the Internet zone security setting to "High"

Setting the Internet zone security setting to "High" will result in the user being prompted before running ActiveX controls and Active Scripting, which may reduce the risk of certain attack vectors.

Disable Active Scripting

Disabling Active Scripting will prevent Active Scripting from running, which may reduce the risk of certain attack vectors.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Vulnerable		2010-03-09

References

http://www.microsoft.com/technet/security/bulletin/ms10-018.mspx
http://www.microsoft.com/technet/security/advisory/981374.mspx
http://support.microsoft.com/kb/927917

Credit

Thanks to Microsoft for reporting this vulnerability.

This document was written by Will Dormann.

Other Information

Date Public:	2010-03-09
Date First Published:	2010-03-09
Date Last Updated:	2010-03-30
CERT Advisory:
CVE-ID(s):	CVE-2010-0806
NVD-ID(s):	CVE-2010-0806
US-CERT Technical Alerts:
Severity Metric:	28.55
Document Revision:	16

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