Vulnerability Note VU#543907

Microsoft Office fails to properly handle specially crafted Rich Text Format files

Overview

A vulnerability in the way Microsoft Office handles Rich Text Format files may lead to execution of arbitrary code.

I. Description

Microsoft Office contains a vulnerability that could be exploited when parsing malformed strings contained in specially crafted Rich Text Format (.rtf) files. According to Microsoft Security Bulletin ms08-026:

The vulnerability could allow remote code execution if a user opens a specially crafted .rtf file with malformed strings in Word or previews a specially crafted .rtf file with malformed strings in rich text e-mail.

II. Impact

A remote, unauthenticated attacker may be able to execute arbitrary code with the privileges of the affected user or cause a denial-of-service condition.

III. Solution

Update

Microsoft has released an update to address this issue. See Microsoft Security Bulletin ms08-026 for more details.

Do not open untrusted Microsoft Office documents

Do not open unfamiliar or unexpected Microsoft Office documents, particularly those hosted on web sites or delivered as email attachments. Please see Cyber Security Tip ST04-010.

Disable automatic opening of Microsoft Office documents

By default, Microsoft Office 97 and Microsoft Office 2000 will configure Internet Explorer to automatically open Microsoft Office documents. This feature can be disabled by using the Office Document Open Confirmation Tool. Mozilla Firefox users should disable automatic opening of files, as specified in the Securing Your Web Browser document.

Do not rely on file name extension filtering

In most cases, Windows will call a Microsoft Office application to open a document even if the document has an unknown file extension. Filtering for common extensions (e.g., .ppt, .xls, and .doc) will not detect all Microsoft Office documents. Additionally, a Microsoft Office file with no file extension will also open with a Microsoft Office application.

Systems Affected

Vendor	Status	Date Updated
Microsoft Corporation	Vulnerable	13-May-2008

References

http://www.microsoft.com/technet/security/bulletin/ms08-026.mspx

Credit

This vulnerability was reported in Microsoft Security Bulletin ms08-026. Microsoft credits wushi of team509, working with Zero Day Initiative, for reporting this issue.

This document was written by Chris Taschner.

Other Information

Date Public	05/13/2008
Date First Published	05/13/2008 02:32:54 PM
Date Last Updated	05/13/2008
CERT Advisory
CVE Name	CVE-2008-1091
US-CERT Technical Alerts
Metric	25.25
Document Revision	10