A complete revision history can be found at the end of this file.
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.
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.
By exploiting either of the buffer overflow vulnerabilities, remote attackers may be able to execute arbitrary code with Local System privileges.
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.
Microsoft has published Microsoft Security Bulletin MS03-039 to address this vulnerability. For more information, please see
http://www.microsoft.com/technet/security/bulletin/MS03-039.asp
This bulletin supersedes MS03-026.
As an interim measure, users can reduce the chance of successful exploitation by blocking traffic to and from well-known Microsoft RPC ports, including
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.
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 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.
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.
We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from
If you prefer to use DES, please call the CERT hotline for more information.
CERT publications and other security information are available from our web site
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Revision History
Sep 10, 2003: Initial release
Sep 10, 2003: Added links to Vulnerability Notes