TSRT-06-05: Computer Associates eTrust AntiVirus WebScan Automatic
            Update Code Execution Vulnerability

http://www.tippingpoint.com/security/advisories/TSRT-06-05.html
August 7, 2006

-- CVE ID:
CVE-2006-3976
CVE-2006-3977

-- Affected Vendor:
Computer Associates

-- Affected Products:
eTrust AntiVirus WebScan v1.1.0.1047 and earlier

-- TippingPoint(TM) IPS Customer Protection:
TippingPoint IPS customers have been protected against this
vulnerability since July 26, 2006 by Digital Vaccine protection
filter ID 4544. For further product information on the TippingPoint IPS:

    http://www.tippingpoint.com 

-- Vulnerability Details:
This vulnerability allows remote attackers to execute arbitrary code on
systems with affected installations of the Computer Associates eTrust
AntiVirus WebScan ActiveX component. Successful exploitation requires
that the target user browse to a malicious web page. The vulnerable
component is typically installed as a prerequisite to the free online
WebScan found at:

    http://www3.ca.com/securityadvisor/virusinfo/scan.aspx

The specific flaw exists during the automatic update process for the
WebScan ActiveX component. WebScan allows the initializing web page to
specify the location that the component will use to download and
install updates through the 'SigUpdatePathFTP' parameter (and
potentially the 'SigUpdatePathHTTP' parameter). It downloads the
'filelist.txt' manifest and acquires any update files it lists. There
is no verification performed by WebScan to assure the authenticity of
the information in the file list or the files themselves. This leads to
a possibility of two unique attacks.

In the first attack (CVE-2006-3976), an attacker compresses a malicious
file, creates a file listing that includes it and then points the update
path to his/her server. The WebScan component will download and
decompress the file on the local system. Other components on the system
may load the file, and certain files (such as arclib.dll and vete.dll)
will be loaded by WebScan itself. If either of these files is replaced
by a malicious version, it becomes possible for an attacker to gain
control of the system WebScan is installed on during the scanner's
initialization process.

In the second attack (CVE-2006-3977), an attacker compresses an
outdated version of a legitimate Computer Associates file, and lists an
inaccurate timestamp for the file in the update server's file listing.
There is no verification on the time/date information provided by the
remote server. It is possible for an attacker to install a legitimate
but extremely outdated version of virus definition files or engine
components to severely limit the scope of the protection provided by
WebScan.

-- Vendor Response:
Computer Associates has addressed this issue in the latest version of
their WebScan product. More information from the vendor is available
at:

    http://www3.ca.com/securityadvisor/vulninfo/vuln.aspx?id=34509

-- Disclosure Timeline:
2006.07.17 - Vulnerability reported to vendor
2006.07.26 - Digital Vaccine released to TippingPoint customers
2006.08.07 - Coordinated public release of advisory

-- Credit:
This vulnerability was discovered by Matthew Murphy, TippingPoint
Security Research Team.

-- About the TippingPoint Security Research Team (TSRT):
The TippingPoint Security Research Team (TSRT) consists of industry
recognized security researchers that apply their cutting-edge
engineering, reverse engineering and analysis talents in our daily
operations. More information about the team is available at:

    http://www.tippingpoint.com/security
 
The by-product of these efforts fuels the creation of vulnerability
filters that are automatically delivered to our customers' intrusion
prevention systems through the Digital Vaccine(R) service.