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- -----Original Message---#
From: Peter Gr?ndl
[mailto:peter.grundl@DEFCOM.COM]
Sent: Wednesday, May 09, 2001 3:49 AM
To: win2ksecadvice@LISTSERV.NTSECURITY.NET
Subject: def-2001-24: Windows 2000 Kerberos DoS

Defcom Labs Advisory def-2001-24

Windows 2000 Kerberos DoS
Author: Peter Gr?ndl
Release Date: 2001-05-09

- ------------------------=[Brief Description]=-------------------------
The Kerberos service and kerberos password service contain a flaw that could allow a malicious attacker to cause a Denial of Service on the Kerberos service and thus making all domain authentication impossible.

------[Affected Systems]=------------
Windows 2000 Server
Windows 2000 Advanced Server
Windows 2000 Datacenter Server
------=[Detailed Description]=--------
By creating a connection to the kerberos service and the disconnecting again, without reading from the socket, the LSA subsystem will leak memory. After about 4000 connections the kerberos service will stop accepting connections to tcp ports 88 (kerberos) and 464 (kpasswd) and all domain authentication will effectively have died (if the target was a domain controller).

It requires a reboot to recover from the attack.

-------=[Workaround]=--------------
Disallow access to TCP ports 88 and 464 from untrusted networks or/and apply the patch located at the following URL:
http://www.microsoft.com/technet/security/bulletin/MS01-024.asp
--------------=[Vendor Response]=----------
This issue was brought to the vendor's attention on the 26th of January, 2001, and the vendor released a patch on the 8th of May.
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This release was brought to you by Defcom Labs
labs@defcom.com http://www.defcom.com/
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