CERT Advisory CA-2003-23 RPCSS Vulnerabilities in Microsoft Windows

From: CERT Advisory (cert-advisory_at_cert.org)
Date: 09/10/03

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    CERT Advisory CA-2003-23 RPCSS Vulnerabilities in Microsoft Windows

       Original release date: September 10, 2003
       Last revised: --
       Source: CERT/CC

       A complete revision history can be found at the end of this file.

    Systems Affected

         * Microsoft Windows NT Workstation 4.0
         * Microsoft Windows NT Server 4.0
         * Microsoft Windows NT Server 4.0, Terminal Server Edition
         * Microsoft Windows 2000
         * Microsoft Windows XP
         * Microsoft Windows Server 2003


       Microsoft has published a bulletin describing three vulnerabilities
       that affect numerous versions of Microsoft Windows. Two of these
       vulnerabilities are remotely exploitable buffer overflows that may
       allow an attacker to execute arbitrary code with system privileges.
       The third vulnerability may allow a remote attacker to cause a denial
       of service.

    I. Description

       The Microsoft RPCSS Service is responsible for managing Remote
       Procedure Call (RPC) messages. There are two buffer overflow
       vulnerabilities in the RPCSS service, which is enabled by default on
       many versions of Microsoft Windows. These buffer overflows occur in
       sections of code that handle DCOM activation messages sent to the
       RPCSS service.

       The CERT/CC is tracking these vulnerabilities as VU#483492 and
       VU#254236, which correspond to CVE candidates CAN-2003-0715 and
       CAN-2003-0528, respectively. The buffer overflows discussed in this
       advisory are different than those discussed in previous advisories.

       Microsoft has also published information regarding a denial-of-service
       vulnerability in the RPCSS service. This vulnerability only affects
       Microsoft Windows 2000 systems.

       The CERT/CC is tracking this vulnerability as VU#326746, which
       corresponds to CVE candidate CAN-2003-0605. This vulnerability was
       previously discussed in CA-2003-19.

    II. Impact

       By exploiting either of the buffer overflow vulnerabilities, remote
       attackers may be able to execute arbitrary code with Local System

       By exploiting the denial-of-service vulnerability, remote attackers
       may be able to disrupt the RPCSS service. This may result in general
       system instability and require a reboot.

    III. Solution

    Apply a patch from Microsoft

       Microsoft has published Microsoft Security Bulletin MS03-039 to
       address this vulnerability. For more information, please see


       This bulletin supersedes MS03-026.

    Block traffic to and from common Microsoft RPC ports

       As an interim measure, users can reduce the chance of successful
       exploitation by blocking traffic to and from well-known Microsoft RPC
       ports, including
         * Port 135 (tcp/udp)
         * Port 137 (udp)
         * Port 138 (udp)
         * Port 139 (tcp)
         * Port 445 (tcp/udp)
         * Port 593 (tcp)

       To prevent compromised hosts from contacting other vulnerable hosts,
       the CERT/CC recommends that system administrators filter the ports
       listed above for both incoming and outgoing traffic.

    Disable COM Internet Services and RPC over HTTP

       COM Internet Services (CIS) is an optional component that allows RPC
       messages to be tunneled over HTTP ports 80 and 443. As an interim
       measure, sites that use CIS may wish to disable it as an alternative
       to blocking traffic to and from ports 80 and 443.

    Disable DCOM

       Disable DCOM as described in MS03-039 and Microsoft Knowledge Base
       Article 825750.

       This document was written by Jeffrey P. Lanza and is based upon the
       information in MS03-039.

       This document is available from:

    CERT/CC Contact Information

       Email: cert@cert.org
              Phone: +1 412-268-7090 (24-hour hotline)
              Fax: +1 412-268-6989
              Postal address:
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              Software Engineering Institute
              Carnegie Mellon University
              Pittsburgh PA 15213-3890

       CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) /
       EDT(GMT-4) Monday through Friday; they are on call for emergencies
       during other hours, on U.S. holidays, and on weekends.

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       Revision History
    Sep 10, 2003: Initial release

    Version: PGP 6.5.8

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