Vulnerability Note VU#587579

MIT Kerberos V5 ASN.1 decoder fails to perform bounds checking on data element length fields

Original Release date: 31 Jan 2003 | Last revised: 04 Apr 2003


The MIT Kerberos V5 implementation contains an ASN.1 decoding flaw that may allow remote attackers to crash affected Kerberos applications.


Kerberos V5 protocol messages are defined using Abstract Syntax Notation One (ASN.1), a formal language that allows protocol specifications to be easily encoded for network transmission. For example, each data element in a given protocol message is encoded with additional information that indicates the type and length of the supplied data. This standardized format allows the recipient of the message to interpret the data elements and handle them appropriately.

The ASN.1 decoder included with MIT Kerberos V5 fails to perform bounds checking on the length values supplied with each data element. In some cases, an incoming message can contain a large unsigned data element length value that is misinterpreted as a negative signed value. When an affected Key Distribution Center (KDC) or other Kerberos application attempts to allocate negative or unreasonably large amounts of storage, an error condition will occur that may cause the application to crash.


This vulnerability allows remote attackers to crash affected applications, resulting in a denial of service condition.


This vulnerability was addressed in MIT Kerberos V5 1.2.5, released on April 30, 2002. MIT krb5 Security Advisory 2003-001 provides additional information from MIT and is available at:

For information regarding other vendors who may be affected, please see the vendor section of this document.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
MandrakeSoftAffected03 Apr 200304 Apr 2003
MIT Kerberos Development TeamAffected04 Apr 200230 Jan 2003
Red Hat Inc.Affected08 Apr 200227 Mar 2003
Hewlett-Packard CompanyNot Affected08 Apr 200231 Jan 2003
Microsoft CorporationNot Affected04 Apr 200231 Jan 2003
Apple Computer Inc.Unknown08 Apr 200229 Jan 2003
BSDIUnknown08 Apr 200229 Jan 2003
Cisco Systems Inc.Unknown08 Apr 200229 Jan 2003
ConectivaUnknown08 Apr 200229 Jan 2003
Cray Inc.Unknown08 Apr 200231 Jan 2003
DebianUnknown08 Apr 200229 Jan 2003
IBMUnknown08 Apr 200231 Jan 2003
KTH KerberosUnknown04 Apr 200229 Jan 2003
NetBSDUnknown08 Apr 200229 Jan 2003
OpenBSDUnknown08 Apr 200229 Jan 2003
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



The reporter of this vulnerability wishes to remain anonymous.

This document was written by Jeffrey P. Lanza.

Other Information

  • CVE IDs: CAN-2002-0036
  • Date Public: 28 Jan 2003
  • Date First Published: 31 Jan 2003
  • Date Last Updated: 04 Apr 2003
  • Severity Metric: 31.50
  • Document Revision: 43


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