Vulnerability Note VU#259798

MIT Kerberos 5 allows unauthenticated attacker to cause MIT krb5 Key Distribution Center to free unallocated memory

Original Release date: 13 Jul 2005 | Last revised: 13 Jul 2005


An unauthenticated attacker can cause MIT krb5 Key Distribution Center (KDC) to free unallocated memory, possibly leading to arbitrary code execution.


Kerberos is a network authentication system which uses a trusted third party (a KDC) to authenticate clients and servers to each other. It is designed to provide strong authentication for client/server applications by using secret-key cryptography. MIT Kerberos code is used in network applications from a variety of different vendors and is included in many UNIX and Linux distributions.

The MIT krb5 Security Advisory 2005-002 issued 2005 July 12, available from
<> states:

    The MIT krb5 Key Distribution Center (KDC) implementation can corrupt the heap by attempting to free memory at a random address when it receives a certain unlikely (but valid) request via a TCP connection. This attempt to free unallocated memory can result in a KDC crash and consequent denial of service. [CAN-2005-1174, VU#259798]
    An unauthenticated attacker may be able to use this vulnerability to execute arbitrary code on the KDC host, potentially compromising an entire Kerberos realm. No exploit code is known to exist at this time. Exploitation of these vulnerabilities is believed to be difficult.


An unauthenticated attacker may be able to execute arbitrary code on the KDC host, potentially compromising an entire Kerberos realm. An unsuccessful attack against this heap corruption vulnerability may result in a denial of service by crashing the KDC process. According to the MIT krb5 Security Advisory 2005-002 this vulnerability affects the KDC implementation in all MIT krb5 releases supporting TCP client connections to the KDC. This includes krb5-1.3 and later releases, up to and including krb5-1.4.1.


Apply patches available from your vendor. Details of the patch are also available from

If patching can not be performed in a timely manner you could consider disabling TCP support in the KDC to avoid this vulnerability.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
Red Hat Inc.Affected10 May 200511 Jul 2005
Sun Microsystems Inc.Affected10 May 200513 Jul 2005
F5 NetworksNot Affected12 May 200517 May 2005
Juniper NetworksNot Affected10 May 200521 Jun 2005
Microsoft CorporationNot Affected10 May 200527 May 2005
Apple Computer Inc.Unknown10 May 200510 May 2005
ConectivaUnknown10 May 200510 May 2005
Cray Inc.Unknown10 May 200517 May 2005
DebianUnknown10 May 200517 May 2005
EMC CorporationUnknown10 May 200517 May 2005
EngardeUnknown10 May 200517 May 2005
FreeBSDUnknown10 May 200517 May 2005
FujitsuUnknown10 May 200517 May 2005
HitachiUnknown10 May 200517 May 2005
HPUnknown10 May 200517 May 2005
If you are a vendor and your product is affected, let us know.View More »

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



This vulnerability was reported by the MIT Kerberos Development Team. The MIT Kerberos Development Team thank Daniel Wachdorf for reporting this vulnerability.

This document was written by Robert Mead based on information in the MIT krb5 Security Advisory 2005-002.

Other Information

  • CVE IDs: CAN-2005-1174
  • Date Public: 12 Jul 2005
  • Date First Published: 13 Jul 2005
  • Date Last Updated: 13 Jul 2005
  • Severity Metric: 11.48
  • Document Revision: 22


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