SECUNIA ADVISORY ID: SA25620

VERIFY ADVISORY: http://secunia.com/advisories/25620/

CRITICAL: Highly critical

IMPACT: DoS, System access

WHERE: >From remote

OPERATING SYSTEM:
Microsoft Windows 2000 Advanced Server - http://secunia.com/product/21/
Microsoft Windows 2000 Datacenter Server - http://secunia.com/product/1177/
Microsoft Windows 2000 Professional - http://secunia.com/product/1/
Microsoft Windows 2000 Server - http://secunia.com/product/20/
Microsoft Windows XP Home Edition - http://secunia.com/product/16/
Microsoft Windows XP Professional - http://secunia.com/product/22/
Microsoft Windows Server 2003 Datacenter Edition - http://secunia.com/product/1175/
Microsoft Windows Server 2003 Enterprise Edition - http://secunia.com/product/1174/
Microsoft Windows Server 2003 Standard Edition - http://secunia.com/product/1173/
Microsoft Windows Server 2003 Web Edition - http://secunia.com/product/1176/
Microsoft Windows Storage Server 2003 - http://secunia.com/product/12399/

DESCRIPTION: A vulnerability has been reported in Microsoft Windows, which can be exploited by malicious people to cause a DoS (Denial of Service) or compromise a vulnerable system.

The vulnerability is caused due to an error within the Secure Channel (Schannel) security package when parsing digital signatures received from a server during the SSL handshake. This can be exploited to execute arbitrary code (Windows XP), cause the system to stop accepting SSL or TLS connections (Windows 2000), or cause the system to restart (Windows 2003) when a user e.g. visits a malicious website.

NOTE: Windows 2000 and 2003 are not exploitable for arbitrary code execution.

SOLUTION: Apply patches.
Windows 2000 SP4: http://www.microsoft.com/downloads/details.aspx?FamilyId=5b8e728c-cb9f-4176-93a0-bf42d6387f93
Windows XP SP2: http://www.microsoft.com/downloads/details.aspx?FamilyId=8615e6f3-415b-4c23-ba52-7eef70a11d77
Windows XP Professional x64 Edition (optionally with SP2): http://www.microsoft.com/downloads/details.aspx?FamilyId=7e994340-c616-4f66-845b-7eaf095e968a
Windows Server 2003 SP1/SP2: http://www.microsoft.com/downloads/details.aspx?FamilyId=39e6c6d2-7e6f-4992-a731-36f44fe2d87f
Windows Server 2003 x64 Edition (optionally with SP2): http://www.microsoft.com/downloads/details.aspx?FamilyId=da424772-079c-4351-9759-8886e0f1ba79
Windows Server 2003 for Itanium-based systems (SP1/SP2): http://www.microsoft.com/downloads/details.aspx?FamilyId=028592ff-2b69-472e-b186-bd2cc76bdfa4

PROVIDED AND/OR DISCOVERED BY: The vendor credits Thomas Lim, COSEINC.

ORIGINAL ADVISORY: MS07-031 (KB935840): http://www.microsoft.com/technet/security/Bulletin/MS07-031.mspx