def-2001-24: Windows 2000 Kerberos DoS

[Peter Gründl <peter.grundl () DEFCOM COM>]

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                  Defcom Labs Advisory def-2001-24

                   Windows 2000 Kerberos DoS

Author: Peter Gründl <peter.grundl () defcom com>
Release Date: 2001-05-09
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------------------------=[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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