Secunia

Three vulnerabilities have been identified in Microsoft Windows, which can be exploited by malicious people to compromise a vulnerable system or cause a DoS (Denial of Service).

The vulnerabilities affect the DCOM (Distributed Component Object Model) interface within the RPCSS Service and are caused due to boundary errors and an unspecified error when handling certain RPC messages.

Two of the vulnerabilities can be exploited to cause heap overflows allowing execution of arbitrary code on a vulnerable system with "Local System" privileges. The third can be exploited to crash the RPCSS service.

Secunia has constructed a vulnerability test, which can be used to check if you are affected by these issues:
http://secunia.com/MS03-039/

NOTE: Secunia would normally rate these kinds of vulnerabilities as "Moderately critical", since systems only should expose RPC services to other systems on a LAN.

However, since the vulnerabilities are similar to the issue exploited by the Blaster worm, which infected numerous systems, the vulnerabilities have been rated as "Highly critical" instead.

A universal exploit for this vulnerability has been released. Secunia has received credible reports that this exploit may cause a DoS on patched systems by exploiting another vulnerability in the handling of RPC requests:
SA9978

Solution
Microsoft has issued patches, which can be installed manually or via WindowsUpdate.
Further details available in Customer Area

Provided and/or discovered by
Barnaby Jack and Riley Hassell, eEye Digital Security.
Yuan Renguang, NSFOCUS Security Team.
Xue Yong Zhi and Renaud Deraison, Tenable Network Security.

Changelog
Further details available in Customer Area

Original Advisory
Microsoft Security Bulletin MS03-039:
http://www.microsoft.com/technet/security/bulletin/MS03-039.asp

NSFOCUS advisory:
http://www.nsfocus.com/english/homepage/research/0306.htm

eEye Digital Security advisory:
http://www.eeye.com/html/Research/Advisories/AD20030910.html

Other references
Further details available in Customer Area

Deep Links
Links available in Customer Area