Office Updates: Beware Evil PowerPoint Documents

Severity: High

10 May, 2011

Summary:

• These vulnerabilities affect: Most current versions of Microsoft PowerPoint for Windows and Mac (ships with Office), except for 2010.
• How an attacker exploits it: By tricking one of your users into opening a malicious PowerPoint document
• Impact: In the worst case, an attacker executes code on your user’s computer, gaining complete control of it
• What to do: Install Microsoft’s PowerPoint updates as soon as possible, or let Microsoft’s automatic update do it for you (Mac update not available yet)

Exposure:

As part of today’s Patch Day, Microsoft released a security bulletin describing two code execution vulnerabilities in most current versions of PowerPoint, which ships with Microsoft Office. The flaws affect both the Windows and Mac versions. However, they do not affect the most recent 2010 version of Office.

Though the two code execution vulnerabilities differ technically, they share the same scope and impact. If an attacker can entice one of your users into downloading and opening a maliciously crafted PowerPoint document, he can exploit either of these vulnerabilities to execute code on a victim’s computer, usually inheriting that user’s level of privileges and permissions. If your user has local administrative privileges, the attacker gains full control of the user’s machine.

Lately, attackers have leveraged malicious Office documents in their targeted email attacks (spear phishing). User often consider Office documents as benign. Yet, criminals can easily leverage these sorts of vulnerabilities to cause malicious office documents to install malware. We recommend, you download, test, and deploy this updates as soon as you can — hopefully, before your users open the wrong document.

Solution Path

Microsoft has released patches for the Windows version of PowerPoint to correct these vulnerabilities. You should download, test, and deploy the appropriate patches throughout your network immediately, or let the Microsoft Automatic Update feature do it for you.

Unfortunately, Microsoft has not yet released the Mac updates yet. They don’t say exactly when they plan to release the Mac update, only that they will when testing is complete.

MS11-036:

PowerPoint update for:

• Office XP w/SP3
• Office 2003 w/SP3
• Office 2007 w/SP2

• Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats

For All WatchGuard Users:

You can configure WatchGuard appliances to block Microsoft Office documents, like PowerPoint files. However, most organizations need to allow these documents in order to conduct business. Therefore, we recommend you patch instead.

Nonetheless, if you want to block Office documents, the video tutorials below explain how to use WatchGuard’s proxy policies to block content by file extensions (such as PPT or PPTX). Keep in mind, blocking files by extension blocks both malicious and legitimate documents.

• Firebox X Edge running 10.x
  • How do I block files with the FTP proxy?
  • How do I block files with the HTTP proxy?
  • How do I block files with the POP3 proxy?
  • How do I block files with the SMTP proxy

• Firebox X Core and X Peak running Fireware 10.x
  • How do I block files with the FTP proxy?
  • How do I block files with the HTTP proxy?
  • How do I block files with the POP3 proxy?
  • How do I block files with the SMTP proxy?

Status:

Microsoft has released PowerPoint updates to fix these vulnerabilities.

References:

• MS Security Bulletin MS11-036

This alert was researched and written by Corey Nachreiner, CISSP.