Veritas Backup Exec Remote Agent NDMLSRVR.DLL DoS Vulnerability

iDEFENSE Security Advisory 06.23.05
www.idefense.com/application/poi/display?id=270&type=vulnerabilities
June 23, 2005

I. BACKGROUND

VERITAS Backup Exec is an advanced backup and restore solution for 
Microsoft Windows server environments. More information is available 
from the vendor's website:

    http://veritas.com/Products/www?c=product&refId=57

II. DESCRIPTION

Remote exploitation of a denial of service condition in Veritas Software
Corp.'s Backup Exec allows attackers to crash the vulnerable service.

The Veritas Backup Exec Agent listens on TCP port 10000 and is
responsible for accepting connections from the backup server when a
backup is to occur. Typically the agent would be installed on most
servers and important workstations in an enterprise environment. Veritas
Backup Exec uses the standard NMDP protocol to communicate with the
listening agents.

The vulnerability specifically exists within NDMLSRVR.DLL due to a null
pointer dereference upon parsing of a maliciously crafted packet at the
following instruction:

    0x01053355 MOVZX EAX, WORD PTR [ESI]

An unhandled exception occurs resulting in a crash of the program and a
denial of service condition.

III. ANALYSIS

Exploitation does not require authentication, thereby allowing any 
remote attacker to cause the denial of service and disruption of backup 
capabilities.

IV. DETECTION

iDEFENSE has confirmed the existence of this vulnerability in Backup
Exec for Windows Servers version 10.0 and 10.0 SP1, the latest versions
available as of this report. It is suspected that older versions are
also vulnerable.

Several vendors ship or use Veritas software including Hitachi and NEC
Corporation.

V. WORKAROUND

Use a firewall to restrict incoming connections to trusted workstations 
running the Backup Exec client software which uses port 10000 TCP.

VI. VENDOR RESPONSE

The vendor has addressed this vulnerability in security advisory
VX05-001:

   http://seer.support.veritas.com/docs/276533.htm

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-0772 to this issue. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

05/13/2005  Initial vendor notification
05/13/2005  Initial vendor response
06/22/2005  Coordinated public disclosure

IX. CREDIT

Sebastian Apelt is credited with this discovery.

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X. LEGAL NOTICES

Copyright (c) 2005 iDEFENSE, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.