[NT] DoS Vulnerability in Microsoft Windows SPNEGO Protocol Decoding (MS04-011)
From: SecuriTeam (support_at_securiteam.com)
Date: 04/18/04
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To: list@securiteam.com Date: 18 Apr 2004 12:15:57 +0200
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DoS Vulnerability in Microsoft Windows SPNEGO Protocol Decoding (MS04-011)
------------------------------------------------------------------------
SUMMARY
Simple and Protected GSS-API Negotiation Mechanism (SPNEGO) protocol is
used to negotiate which security mechanism should be adopted. Windows
system allows various authentication mechanisms, it also uses SPNEGO
protocol to implement the authentication mechanism negotiation between the
clients and servers.
There is a security vulnerability when Windows system handles SPNEGO
protocol codes, which allows attackers to launch DoS attacks.
When a carefully crafted SPNEGO NegTokenInit request is sent, a null
pointer reference error might occur in LSASRV.DLL, resulting in LSASS.EXE
crash. This will make all the operations related to system authentication
(such as remote access to SMB share, or interactive local login)
unavailable. For Windows 2003, it will result in automatic shutting off or
bluescreen.
Attackers can launch attacks through any service that uses SPNEGO, such as
TCP port 139, 445. By default IIS also negotiates which authentication
protocol (for example, NTLM, Kerberos, etc)should be adopted by SPNEGO,
therefore it's possible for attackers to launch attacks through IIS.
From vendor's response the same type of malformed request could still have
triggered a buffer overflow issue in the subsequent code, if they were to
have only fixed the DoS issue. Vendor's patch fixes both the DoS and
buffer overflow issues.
DETAILS
Impact:
NSFOCUS Security Team has found there is a remote DoS vulnerability in the
SPNEGO protocol decoding function of Microsoft Windows system. Exploiting
the vulnerability remote attackers could cause Windows system to crash or
malfunction.
Workaround:
* Restrict access to the following ports from untrusted IPs at the
firewall:
445/UDP
139/TCP
445/TCP
* For the system that is providing WEB service through IIS, either of the
following methods can be used to mitigate the threat:
1. Disable "Integrated windows authentication" in IIS service
2. Disable authentication negotiation. Only allow authentication through
NTLM by the following command:
cscript adsutil.vbs set w3svc/NTAuthenticationProviders "NTLM"
adsutil.vbs can be found in the adminscripts directory of IIS.
More detail is available at:
<http://support.microsoft.com/?id=215383>
http://support.microsoft.com/?id=215383
Vendor Status:
2004.02.19 Informed the vendor
2004.02.19 Vendor confirmed the vulnerability
2004.04.13 Microsoft released a security bulletin (MS04-011) and relative
patches for the vulnerability.
Detailed information for the Microsoft security bulletin is available at:
<http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx>
http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx`
ADDITIONAL INFORMATION
The information has been provided by <mailto:security@nsfocus.com> Chen
Qing of NSFOCUS Security Team.
The original article can be found at:
<http://www.nsfocus.com/english/homepage/research/0401.htm>
http://www.nsfocus.com/english/homepage/research/0401.htm
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