Vulnerable Systems:
* Windows XP
* Windows XP SP1
* Windows XP SP2
* Windows 2003
* Windows 2003 SP1
* Windows 2000 SP4 when jgdw400.dll installed
Internet Explorer supports Johnson-Grace compressed images, or .art files. Johnson-Grace developed this technology in 1991. In 1994, American Online Inc. began using the technology and, in 1996, purchased the company to secure rights to it. It is now licensed to Microsoft for usage in Internet Explorer by way of the jgdw400.dll dynamically linked library, which is copyrighted by AOL.
The vulnerability specifically exists due to improper parsing of a malformed .art file during rendering. With a carefully crafted .art file, it is possible to overwrite portions of the heap with static values from a file independent table in memory. Although this typically would be somewhat limiting from an exploitation standpoint, in this case an attacker can utilize large images or JavaScript to fill the heap so that these static values reliably point into controlled regions. Because there are an abundance of function pointers on the heap that an attacker may smash, heap integrity checks are not effective in preventing
exploitation.
Successful exploitation of this vulnerability allows attackers to execute arbitrary code with the privileges of the currently logged-on user. iDefense Labs analysis has shown that exploitation can be as reliable as 75 percent with the current exploitation method. Upon failed exploitation attempts, the system may become slow or unresponsive due to the method employed by the exploit to fill memory in order to facilitate an exploitable memory state.
It should be noted that hardware data execution prevention (DEP) will prevent exploitation from occurring by the iDefense Labs-maintained exploit code. This is a result of the payload executing on the heap, which is marked writable and thus not executable.
It should also be noted that the file does NOT need to have an .art extension to be rendered by the vulnerable library. Any extension can be used, provided the image is loaded via an IMG SRC tag in an HTML document in Internet Explorer.
Workaround:
Remove the following dynamically linked libraries from:
C:\windows\system32\jgpl400.dll
C:\windows\system32\jgdw400.dll
C:\windows\system32\jgaw400.dll
C:\windows\system32\jgsd400.dll
C:\windows\system32\jgmd400.dll
C:\windows\system32\jgsh400.dll
This will effectively disable the viewing of all .ART files on the system.
