Adobe Plugs Four Flash Security Holes on Patch Day

Summary:

  • This vulnerability affects: Adobe Flash Player  11.6.602.171 and earlier, running on all platforms
  • How an attacker exploits it: By enticing users to visit a website containing malicious Flash content
  • Impact: In the worst case, an attacker can execute code on the user’s computer, potentially gaining control of it
  • What to do: Download and install the latest version of Adobe Flash Player (version 11.6.602.180 for PC and Mac)

Exposure:

Adobe Flash Player displays interactive, animated web content called Flash. Although Flash is optional, 99% of PC users download and install it to view multimedia web content. It runs on many operating systems, including mobile operating systems like Android.

In a security bulletin released yesterday, Adobe announced a patch that fixes four critical vulnerabilities in their popular Flash Player. Though the flaws differ technically, they all consist of memory corruption issues, including a buffer overflow flaw, a  use after free issue, an integer overflow and so on. The issues share the same general impact. If an attacker can entice one of your users to visit a malicious website, or into handling specially crafted Flash (SWF of FLV) content, he could exploit these flaws to execute code on that user’s computer, with that user’s privileges. If your users have administrator privileges, the attacker could gain full control of their computers.

The good news is, unlike the emergency Flash update two weeks ago, attackers don’t seem to be exploiting these flaws in the wild right now. Nonetheless, Adobe rates the update as a “Priority 1” for Windows users, and recommends you apply the it as soon as possible (within 72 hours). We have noticed that attackers and researchers seem to be finding holes in Flash as often as they are Java. Whatever platform you run it on, we highly recommend you keep Flash up to date.

Solution Path

Adobe has released new versions of Flash Player (11.6.602.180 for PC and Mac) to fix these issues. If you allow Adobe Flash in your network, you should download and install the new versions immediately. If you’ve enabled Flash Player’s recent “silent update” option, you will receive this update automatically.

  • Download Flash Player for your computer:
Also, we believe attackers and researchers have been focusing on exploit Flash lately (like they have focused on Java). Flash is used on many web sites, so it may be difficult to make your users remove it. However, there are script limiting plugins, such as NoScript and NotScripts, which prevents Flash, and other languages  from running by default on web sites. This allows your users to create a whitelist of trusted sites, and only run Flash when absolutely necessary. In doing so, you can prevent many drive-by download attacks that might leverage these sorts of Flash flaws.
NOTE: Chrome ships with its own version of Flash, built-in. If you use Chrome as you web browser, you will also have to update it separately, though Chrome often receive its updates automatically.

For All WatchGuard Users:

If you choose, you can configure the HTTP proxy on your XTM appliance to block Flash content. Keep in mind, doing so blocks all Flash content, whether legitimate or malicious.

Our proxies offer many ways for you to block files and content, including by file extensionMIME type, or by using very specific hexidecimal patterns found in the body of a message – a technique sometimes referred to as Magic Byte detection. Below I list the various ways you can identify various Flash files:

File Extension:

  • .swf – Shockwave
  • .flv –  Adobe Flash file (file typically used on websites)
  • .fla – Flash movie file
  • .f4v – Flash video file
  • .f4p – Protected Flash video file
  • .f4a – Flash audio file
  • .f4b – Flash audiobook file

MIME types:

  • video/x-flv
  • application/x-shockwave-flash
  • application/x-shockwave-flash2-preview
  • application/futuresplash
  • image/vnd.rn-realflash

FILExt.com reported Magic Byte Pattern:

  • Hex SWF: 46 57 53
  • ASCII SWF: FWS

(Keep in mind, not all the Hex and ASCII patterns shared here are appropriate for content blocking. If the pattern is too short, or not unique enough, blocking with them could result in many false positives) 

If you decide you want to block Flash files, the links below contain instructions that will help you configure your Firebox proxy’s content blocking features using the file and MIME information listed above.

Status:

Adobe has released updates to fix these Flash vulnerabilities.

References:

This alert was researched and written by Corey Nachreiner, CISSP (@SecAdept)

About Corey Nachreiner

Corey Nachreiner has been with WatchGuard since 1999 and has since written more than a thousand concise security alerts and easily-understood educational articles for WatchGuard users. His security training videos have generated hundreds of letters of praise from thankful customers and accumulated more than 100,000 views on YouTube and Google Video. A Certified Information Systems Security Professional (CISSP), Corey speaks internationally and is often quoted by other online sources, including C|NET, eWeek, and Slashdot. Corey enjoys "modding" any technical gizmo he can get his hands on, and considers himself a hacker in the old sense of the word.

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