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CERT Advisory CA-2003-19 Exploitation of Vulnerabilities in Microsoft RPC
Interface

   Original issue date: July 31, 2003
   Last revised: -
   Source: CERT/CC

   A complete revision history is at the end of this file.

Systems Affected

     * Microsoft Windows NT 4.0
     * Microsoft Windows NT 4.0 Terminal Services Edition
     * Microsoft Windows 2000
     * Microsoft Windows XP
     * Microsoft Windows Server 2003

Overview

   The   CERT/CC   is   receiving  reports  of  widespread  scanning  and
   exploitation  of  two recently discovered vulnerabilities in Microsoft
   Remote Procedure Call (RPC) Interface.

I. Description

   Reports  to  the CERT/CC indicate that intruders are actively scanning
   for  and  exploiting a vulnerability in Microsoft's DCOM RPC interface
   as  described  in VU#568148 and CA-2003-16. Multiple exploits for this
   vulnerability  have  been  publicly  released,  and  there  is  active
   development   of   improved  and  automated  exploit  tools  for  this
   vulnerability.  Known  exploits  target  TCP  port  135  and  create a
   privileged  backdoor  command shell on successfully compromised hosts.
   Some  versions  of the exploit use TCP port 4444 for the backdoor, and
   other  versions  use  a  TCP  port number specified by the intruder at
   run-time.  We  have  also  received  reports  of scanning activity for
   common  backdoor ports such as 4444/TCP. In some cases, due to the RPC
   service  terminating,  a  compromised  system  may  reboot  after  the
   backdoor is accessed by an intruder.

   There  appears  to  be  a  separate denial-of-service vulnerability in
   Microsoft's  RPC  interface  that  is  also  being  targeted. Based on
   current  information,  we  believe  this vulnerability is separate and
   independent  from  the  RPC  vulnerability  addressed in MS03-026. The
   CERT/CC  is tracking this additional vulnerability as VU#326746 and is
   continuing  to work to understand the issue and mitigation strategies.
   Exploit  code  for  this  vulnerability has been publicly released and
   also targets TCP port 135.

   In  both  of the attacks described above, a TCP session to port 135 is
   used  to  execute the attack. However, access to TCP ports 139 and 445
   may also provide attack vectors and should be considered when applying
   mitigation strategies.

II. Impact

   A  remote  attacker  could  exploit  these  vulnerabilities to execute
   arbitrary  code  with  Local System privileges or to cause a denial of
   service condition.

III. Solutions

Apply patches

   All users are encouraged to apply the patches referred to in Microsoft
   Security  Bulletin  MS03-026  as soon as possible in order to mitigate
   the  vulnerability  described  in  VU#568148.  These  patches are also
   available via Microsoft's Windows Update service.

   Systems  running  Windows  2000  may still be vulnerable to at least a
   denial  of  service  attack via VU#326746 if their DCOM RPC service is
   available  via the network. Therefore, sites are encouraged to use the
   packet  filtering  tips  below  in  addition  to  applying the patches
   supplied in MS03-026.

Filter network traffic

   Sites  are  encouraged  to  block network access to the RPC service at
   network  borders. This can minimize the potential of denial-of-service
   attacks  originating from outside the perimeter. The specific services
   that should be blocked include
     * 135/TCP
     * 135/UDP
     * 139/TCP
     * 139/UDP
     * 445/TCP
     * 445/UDP

   If  access  cannot  be  blocked  for  all  external hosts, the CERT/CC
   recommends  limiting  access  to  only those hosts that require it for
   normal  operation. As a general rule, the CERT/CC recommends filtering
   all  types  of  network  traffic  that  are  not  required  for normal
   operation.

   Because  current exploits for VU#568148 create a backdoor, which is in
   some  cases  4444/TCP, blocking inbound TCP sessions to ports on which
   no  legitimate  services  are  provided  may  limit intruder access to
   compromised hosts.

Recovering from a system compromise

   If  you  believe  a  system under your administrative control has been
   compromised, please follow the steps outlined in

          Steps for Recovering from a UNIX or NT System Compromise

Reporting

   The  CERT/CC is tracking activity related to exploitation of the first
   vulnerability  (VU#568148)  as CERT#27479 and the second vulnerability
   (VU#326746)  as CERT#24523. Relevant artifacts or activity can be sent
   to cert@cert.org with the appropriate CERT# in the subject line.

Appendix A. Vendor Information

   This  appendix  contains information provided by vendors. When vendors
   report  new  information,  this section is updated and the changes are
   noted  in  the  revision  history. If a vendor is not listed below, we
   have not received their comments.

Microsoft

     Please see Microsoft Security Bulletin MS03-026.

Appendix B. References

     * CERT/CC Vulnerability Note VU#561284 -
       https://www.kb.cert.org/vuls/id/561284
     * CERT/CC Vulnerability Note VU#326746 -
       https://www.kb.cert.org/vuls/id/326746
     * Microsoft Security Bulletin MS03-026 -
       https://microsoft.com/technet/security/bulletin/MS03-026.asp
     * Microsoft      Knowledge      Base      article      823980      -
       https://support.microsoft.com?kbid=823980
   ______________________________________________________________________

   Authors: Chad Dougherty and Kevin Houle
   ______________________________________________________________________

   This document is available from:
   https://www.cert.org/advisories/CA-2003-19.html
   ______________________________________________________________________

CERT/CC Contact Information

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          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
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   Revision History

   July 31, 2003: Initial release

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