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Veritas Backup Exec Agent Error Status Remote DoS Vulnerability iDEFENSE Security Advisory 06.23.05 www.idefense.com/application/poi/display?id=271&type=vulnerabilitie s 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 Exploitation of a buffer overflow vulnerability in Veritas Software Corp.'s Backup Exec allows remote attackers to execute arbitrary code. 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 because of improper handling of request packets with an unexpected "Error Status" value. Specifically, any Error Status other than "0" will cause a null pointer dereference, resulting in an unhandled exception as can be seen as follows. eax=00000000 ebx=0032ac08 ecx=00000000 edx=0098a930 esi=0032e1e8 edi=009b5770 eip=008f1c84 esp=00fbfb58 ebp=0032ac30 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010202 *** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\Program Files\VERITAS\Backup Exec\NT\ndmpsrvr.dll - ndmpsrvr+0x21c84: 008f1c84 8b00 mov eax,[eax] ds:0023:00000000=???????? The unhandled exception will result 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 versions 9.0, 9.1 and 10.0. It is suspected that other 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 advisories VX05-001 and VX05-008: http://seer.support.veritas.com/docs/276533.htm http://seer.support.veritas.com/docs/277485.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 03/16/2005 Initial vendor notification 03/30/2005 Initial vendor response 06/22/2005 Coordinated public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright (c) 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@idefense.com for permission. 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.