CERT warns for exploitation of RPC
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.
