Adobe Flash is a multimedia platform. It is used to add animation, video, and interactivity to web pages, PDF files or even Microsoft Office documents.

Adobe Flash supports a scripting language called ActionScript; it is executed by the ActionScript Virtual Machine. ActionScript code is typically compiled into bytecode format called ActionScript Byte Code (ABC). The bytecode verifier is responsible for safety check, making sure there is no type-unsafe operations, stack underflow/overflow, improper array accesses, etc.

A type confusion vulnerability exists in Adobe Flash Player ActionScript Virtual Machine. Specifically, the flaw exists in the implementation of callMethod bytecode command. The bytecode verifier fails to detect the stack misalignment under certain circumstances. An attacker can exploit this vulnerability by enticing a user to visit a crafted web page, open a crafted PDF file or open a crafted Office document; all of which may contain malicious Adobe Flash content. Successful exploitation would allow for arbitrary code execution with the privileges of the currently logged in user.

The vulnerability has been assigned as CVE-2011-0611.

SonicWALL has released several IPS signatures to detect and block known exploits targeting this vulnerability. The following signatures were released to address this issue:

• 6475 – Adobe Flash Player ActionScript callMethod Type Confusion 1

• 6476 – Adobe Flash Player ActionScript callMethod Type Confusion 2