A complete revision history is at the end of this file.
A buffer overflow vulnerability exists in the Win32 API libraries shipped with all versions of Microsoft Windows 2000 and Microsoft Windows NT 4.0. This vulnerability, which is being actively exploited on WebDAV-enabled IIS 5.0 servers, will allow a remote attacker to execute arbitrary code on unpatched systems. Sites running Microsoft Windows 2000 and Microsoft Windows NT 4.0 should apply a patch or disable WebDAV services as soon as possible.
Microsoft Windows 2000 (and possibly prior versions of Windows) contains a dynamic link library (DLL) named ntdll.dll. This DLL is a core operating system component used to interact with the Windows kernel. A buffer overflow vulnerability exists in ntdll.dll, which is utilized by many different components in the Windows operating system.
The WebDAV (RFC2518)
component of Microsoft
IIS 5.0 is an example of one Windows component that uses
ntdll.dll. The IIS WebDAV component utilizes ntdll.dll when
processing incoming WebDAV requests. By sending a specially crafted
WebDAV request to an IIS 5.0 server, an attacker may be able to
execute arbitrary code in the Local System security context,
essentially giving the attacker complete control of the system.
Because the vulnerable Win32 API component is utilized by many other applications, it is possible other exploit vectors exist. However, we have only been told of systems compromised running IIS 5.0 with WebDAV enabled. Sites using Windows 2000 but not running IIS 5.0 with WebDAV need to carefully weigh the trade-offs before applying patches to systems where the core vulnerability exists but may not be exploitable.
Microsoft has issued the following bulletin regarding this vulnerability:Any attacker who can reach a vulnerable web server can gain complete control of the system and execute arbitrary code in the Local System security context. Note that this may be significantly more serious than a simple "web defacement."
A patch is available from Microsoft at
This appendix contains information provided by vendors. When vendors report new information, this section is updated and the changes are noted in the revision history. If a vendor is not listed below, we have not received their comments.
Please see Microsoft Security Bulletin MS03-007.
CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends.
We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from
If you prefer to use DES, please call the CERT hotline for more information.
CERT publications and other security information are available from our web site
To subscribe to the CERT mailing list for advisories and bulletins, send email to
majordomo@cert.org. Please include in the body of your
message
subscribe cert-advisory
* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.
NO WARRANTY
Any material furnished by Carnegie Mellon University and the
Software Engineering Institute is furnished on an "as is"
basis. Carnegie Mellon University makes no warranties of any kind,
either expressed or implied as to any matter including, but not
limited to, warranty of fitness for a particular purpose or
merchantability, exclusivity or results obtained from use of the
material. Carnegie Mellon University does not make any warranty of any
kind with respect to freedom from patent, trademark, or copyright
infringement.
Copyright 2003 Carnegie Mellon University.
Revision History
March 17, 2003: Initial release
March 17, 2003: Changed overview section to reflect IIS 5.0 enabled by default on Windows 2000 server products
March 19, 2003: Changed title from "Buffer Overflow in Microsoft IIS 5.0" to "Buffer Overflow in Core Microsoft Windows DLL"
March 19, 2003: Changed overview and description to reflect fact that vulnerability is in core system DLL
March 19, 2003: Revised section on disabling IIS
April 25, 2003: Revised Systems affected to include Microsoft Windows NT 4.0