Public Vulnerability Reports

Computer Associates BrightStor ARCserve Backup RPC Engine PFC Request Buffer Overflow Vulnerability

01.11.07

BACKGROUND

ARCServer is a backup and recovery management utility used to ensure high availability of critical applications and data. More information can be found on the vendor's website:

http://www3.ca.com/solutions/ProductFamily.aspx?ID=115

DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in Computer Associates International Inc.'s (CA) BrightStor ARCserve Backup v11.5 may allow attackers to execute arbitrary code.

The vulnerability exists within a DLL (ASCORE.dll) used by the the message engine process, msgeng.exe. This process is responsible for handling RPC requests on TCP ports 6503 and 6504.

The vulnerability exists within the handler for opcode 47. This opcode is used to run the PFC, preflight check, utility. PFC is used to run a series of checks on the server to test if any backup jobs might fail.

When parsing a request, the handler passes a user supplied buffer to the vsprintf() function without first validating the buffer size. An attacker may leverage this to trigger an exploitable stack-based buffer overflow condition.

ANALYSIS

Exploitation allows unauthenticated attackers to execute arbitrary code with system-level privileges. Exploitation requires that attackers send a malformed RPC request with opcode number 47. Exploitation is simple, as attackers can utilize SEH-based exploitation methods by triggering an exception when copying data past the end of the stack segment.

DETECTION

iDefense has confirmed the existence of this vulnerability in CA BrightStor ARCServe Backup version 11.5 on Windows. Previous versions may also be affected.

WORKAROUND

Employing firewalls to restrict access to the aforementioned ports will prevent the vulnerable code from being reached.

VENDOR RESPONSE

Computer Associates has addressed this vulnerability with patches to the vulnerable software. For more information, please consult their advisory at the following URL.

http://supportconnectw.ca.com/public/storage/infodocs/babimpsec-notice.asp

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-0169 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

01/03/2007 Initial vendor notification
01/04/2007 Initial vendor response
01/11/2007 Coordinated public disclosure

CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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LEGAL NOTICES

Copyright © 2006 Verisign, Inc.

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