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UNIRAS ALERT - 18/03 - Microsoft - Buffer Overrun In RPC Interface Could Allow Code Execution (UPDATE!)



 
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   UNIRAS (UK Govt CERT) ALERT - 18/03 dated 18.07.03  Time: 14:15
 UNIRAS is part of NISCC(National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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Title
=====

UPDATE!

Originally issued as part of Briefing 410/03.
Additional information contained within this Alert. 

Microsoft Security Bulletin - MS03-026:
Buffer Overrun In RPC Interface Could Allow Code Execution.
            
UNIRAS COMMENT:
===============

Departmental and company security officers are strongly recommended to apply 
the patch for the vulnerability discussed in Microsoft security bulletin 
MS03-026. This vulnerability, a stack based buffer overflow in Windows RPC
services, could enable an attack to compromise a remote computer with 
access as the local SYSTEM user. This vulnerability affects all Microsoft 
Windows systems. Claims of the existence of proof-of-concept exploits have
been published, and it is highly likely that working exploits of this 
vulnerability will be developed soon, if they are not already available. Patches
should be applied, as soon as they have been tested on a non-operational system, 
to all Microsoft Windows systems.

The patch is available at:

http://www.microsoft.com/technet/security/bulletin/ms03-026.asp
http://www.microsoft.com/security/security_bulletins/ms03-026.asp

As is best practice, organisational firewalls should be configured to deny all
services that are not explicitly allowed. However, in this case, block TCP/UDP
ports 135, and TCP ports 139, 445 and 593 on your organisational perimeter 
firewalls if they are open.

This is because the vulnerability lies in one of the RPC interfaces that the endpoint
mapper/RPCSS services. As such, it is accessible over any RPC protocol sequence that 
the endpoint mapper listens on (i.e. TCP and UDP port 135, TCP ports 139, 445 and 593). 

Reference: tsabin@xxxxxxxxxxxxxxxxxx

http://archives.neohapsis.com/archives/yesterday/0020.html

Detail
====== 

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Title:      Buffer Overrun In RPC Interface Could Allow Code 
            Execution (823980)

Date:       16 July 2003
Software:   Microsoft(r) Windows (r) NT 4.0
            Microsoft Windows NT 4.0 Terminal Services Edition 
            Microsoft Windows 2000 
            Microsoft Windows XP 
            Microsoft Windows Server 2003 
Impact:     Run code of attacker's choice
Max Risk:   Critical
Bulletin:   MS03-026

Microsoft encourages customers to review the Security Bulletins 
at: 
http://www.microsoft.com/technet/security/bulletin/MS03-026.asp
http://www.microsoft.com/security/security_bulletins/MS03-026.asp
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Issue:
======

Remote Procedure Call (RPC) is a protocol used by the Windows 
operating system. RPC provides an inter-process communication 
mechanism that allows a program running on one computer to 
seamlessly execute code on a remote system. The protocol itself 
is derived from the OSF (Open Software Foundation) RPC protocol, 
but with the addition of some Microsoft specific extensions. 

There is a vulnerability in the part of RPC that deals with 
message exchange over TCP/IP. The failure results because of 
incorrect handling of malformed messages. This particular 
vulnerability affects a Distributed Component Object Model (DCOM) 
interface with RPC, which listens on TCP/IP port 135. This 
interface handles DCOM object activation requests sent by client 
machines (such as Universal Naming Convention (UNC) paths) to the 
server. 

To exploit this vulnerability, an attacker would need to send a 
specially formed request to the remote computer on port 135. 


Mitigating factors: 
====================

 - To exploit this vulnerability, the attacker would require the 
ability to send a specially crafted request to port 135 on the 
remote machine. For intranet environments, this port would 
normally be accessible, but for Internet connected machines, the 
port 135 would normally be blocked by a firewall. In the case 
where this port is not blocked, or in an intranet configuration, 
the attacker would not require any additional privileges. 

 - Best practices recommend blocking all TCP/IP ports that are 
not actually being used. For this reason, most machines attached 
to the Internet should have port 135 blocked. RPC over TCP is not 
intended to be used in hostile environments such as the internet. 
More robust protocols such as RPC over HTTP are provided for 
hostile environments.

Risk Rating:
============
Critical

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read 
the  Security Bulletins at
   
http://www.microsoft.com/technet/security/bulletin/ms03-026.asp
http://www.microsoft.com/security/security_bulletins/ms03-026.asp
   
   for information on obtaining this patch.


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THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS 
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT 
DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING 
THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS 
BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, 
INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL 
DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN 
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT 
ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL 
OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

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Reprinted with permission of Microsoft Corporation.
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UNIRAS wishes to acknowledge the contributions of Microsoft for the information
contained in this Briefing. 
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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
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UNIRAS is a member of the Forum of Incident Response and Security Teams (FIRST) 
and has contacts with other international Incident Response Teams (IRTs) in 
order to foster cooperation and coordination in incident prevention, to prompt 
rapid reaction to incidents, and to promote information sharing amongst its 
members and the community at large. 
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<End of UNIRAS Briefing>
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