Vulnerability Note VU#323172

Microsoft Windows browser election message kernel pool overflow

Overview

A vulnerability exists in the way the Microsoft Windows browser service handles Browser Election messages.

I. Description

From Description of the Microsoft Computer Browser Service:

"The browser service maintains a list of the domain name or workgroup name the computer is in, and the protocol being used for each computer on the network segment being served by the computer running the browser service. On each network segment, a master browser is elected from the group of computers located on the segment that are running the browser service."

The computer browser service protocol driver contains an integer underflow error in browser election message handling, which can cause a kernel pool buffer overrun resulting in memory corruption.

The vulnerable code is only reached if the computer is the Master Browser. However, according to the Microsoft Security Research and Defense blog, the election of the Master Browser varies depending on network configuration:

"In normal enterprise networks the Primary Domain Controller (PDC) will become Master Browser, but depending on the network configuration, other computers on the network can become Master Browser, and therefore be vulnerable. A single system will be Master Browser at any point in time."

For more information, please see Microsoft Security Bulletin MS11-019.

II. Impact

Using a specially crafted Browser Election message, an attacker may be able to cause a Denial of Service (DoS) or execute arbitrary code.

III. Solution

Apply an update

Microsoft addresses this vulnerability with the updates listed in Microsoft Security Bulletin MS11-19.

Restrict Access

Restrict access to the server's broadcast domain and block UDP ports 137, 138 and TCP ports 139, 445 at the network perimeter using firewall rules.

Vendor Information

Vendor	Status	Date Notified	Date Updated
Microsoft Corporation	Affected		2011-04-15

References

http://www.microsoft.com/technet/security/bulletin/MS11-019.mspx
http://blogs.technet.com/b/mmpc/archive/2011/02/16/my-sweet-valentine-the-cifs-browser-protocol-heap-corruption-vulnerability.aspx
http://blogs.technet.com/b/srd/archive/2011/02/16/notes-on-exploitability-of-the-recent-windows-browser-protocol-issue.aspx
http://lists.grok.org.uk/pipermail/full-disclosure/2011-February/079189.html

Credit

This document was written by David Warren.

Other Information

Date Public:	2011-02-14
Date First Published:	2011-02-16
Date Last Updated:	2011-04-15
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Severity Metric:	18.73
Document Revision:	17