Software Engineering Institute

The CAB file decomposer component that is used by multiple Symantec Antivirus products fails to properly handle malformed CAB files, which can result in memory corruption. Successful exploitation may result in arbitrary code execution as the result of a file being scanned. We have confirmed that Symantec Endpoint Protection 11, which uses dec_abi.dll, and Symantec Scan Engine 5.2, which uses Dec2CAB.dll, are affected. Symantec also reports that Symantec Endpoint Endpoint Protection 12.0, AntiVirus Corporate Edition 10.x, and Symantec Scan Engine 5.2.7.x and prior are affected.

A remote, unauthenticated attacker may be able to execute arbitrary code with SYSTEM privileges on a vulnerable system.

Apply an update

Symantec Endpoint Protection 11.0.5 through 11.0.7 MP3 users should apply the Decomposer Update Tool listed in Symantec Advisory SYM12-017. Symantec Endpoint Protection 12.0 and Symantec AntiVirus Corporate Edition users should update to Symantec Endpoint Protection version 12.1. Symantec Scan Engine users should update to version 5.2.8 or Symantec Protection Engine for Cloud Services 7.0.x. Please see Symantec Advisory SYM12-017 for more details.

Use the Microsoft Enhanced Mitigation Experience Toolkit

The Microsoft Enhanced Mitigation Experience Toolkit (EMET) can be used to help prevent exploitation of this vulnerability. CERT/CC has created a video tutorial for setting up EMET 3.0 on Windows 7. Note that platforms that do not support ASLR, such as Windows XP and Windows Server 2003, will not receive the same level of protection that modern Windows platforms will.

Enable DEP in Microsoft Windows

Consider enabling Data Execution Prevention (DEP) in supported versions of Windows. DEP should not be treated as a complete workaround, but it can mitigate the execution of attacker-supplied code in some cases. Microsoft has published detailed technical information about DEP in Security Research & Defense blog posts "Understanding DEP as a mitigation technology" part 1 and part 2. DEP should be used in conjunction with the application of patches or other mitigations described in this document.

Note that when relying on DEP for exploit mitigation, it is important to use a system that supports Address Space Layout Randomization (ASLR) as well. ASLR is not supported by Windows XP or Windows Server 2003 or earlier. ASLR was introduced with Microsoft Windows Vista and Windows Server 2008. Please see the Microsoft SRD blog entry: On the effectiveness of DEP and ASLR for more details.