The SANS Internet Storm Center has raised it’s global Infocon status to yellow due to a recent Exploit targeting a specific DLL on Microsoft Windows Operating Systems. The Explotit, for which there is no official Patch at the moment, allows attackers to execute any kind of code via just by viewing an Image. That means you do not need to open an Image sent to you by mail the malicous code will execute immediately.
- Why is this issue so important? The WMF vulnerability uses images (WMF images) to execute arbitrary code. It will execute just by viewing the image. In most cases, you don’t have click anything. Even images stored on your system may cause the exploit to be triggered if it is indexed by some indexing software. Viewing a directory in Explorer with ‘Icon size’ images will cause the exploit to be triggered as well.
- Is it better to use Firefox or Internet Explorer? Internet Explorer will view the image and trigger the exploit without warning. New versions of Firefox will prompt you before opening the image. However, in most environments this offers little protection given that these are images and are thus considered ‘safe’.
- What versions of Windows are affected? All. Windows 2000, Windows XP, (SP1 and SP2), Windows 2003. All are affected to some extent. Mac OS X, Unix or BSD is not affected. Note: If you’re still running on Win98/ME, this is a watershed moment: we believe (untested) that your system is vulnerable and there will be no patch from MS. Your mitigation options are very limited. You really need to upgrade.
- What can I do to protect myself?
- Microsoft has not yet released a patch. An unofficial patch was made available by Ilfak Guilfanov. The reviewed and tested version is available here (now at v1.3, MD5: 14d8c937d97572deb9cb07297a87e62a), PGP signature (signed with ISC key) here. THANKS to Ilfak Guilfanov for providing the patch!!
- You can unregister the related DLL.
- Virus checkers provide some protection.
To unregister the DLL:
- Click Start, click Run, type “regsvr32 -u %windir%\system32\shimgvw.dll” (without the quotation marks), and then click OK.
- A dialog box appears to confirm that the un-registration process has succeeded. Click OK to close the dialog box.
It is generally considered best practice to unregister the DLL and install the Patch.
For the most up-to-date information and current Patch versions, refer to the WMF FAQ.