Denial of Service in Windows 2000 Kerberos Service

Reported May 09, 2001, by Defcom Labs.


  • Microsoft Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server

A Denial of Service (DoS) condition exists in the Windows 2000 Kerberos and Kerberos password services that can let a potential attacker disrupt logon on requests and Kerberos ticket granting. By repeatedly connecting to the Kerberos services on TCP ports 88 and 464, and not reading from the socket, an attacker can cause the Local Security Authority (LSA) subsystem to leak memory. After the attacker has made approximately 4000 of these connections, the Kerberos system quits responding completely. To regain system functionality, an administrator has to reboot the system.


VENDOR RESPONSE The vendor, Microsoft, acknowledges this vulnerability and recommends that users apply the patch contained in Security Bulletin MS01-024. Users can also disallow access to Kerberos-related TCP ports 88 and 464 from untrusted networks.

Discovered by Peter Gründl.

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