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isakmpd fails to handle ISAKMP packets with "Payload Length" of zero

Vulnerability Note VU#349113

Original Release Date: 2004-08-27 | Last Revised: 2004-08-27


A vulnerability exists in the isakmpd that could allow a remote attacker to cause a denial of service.


The OpenBSD isakmpd establishes security associations for encrypted and authenticated (IPsec) network traffic. It implements the Internet Security Association and Key Management Protocol (ISAKMP) and Internet Key Exchange (IKE) protocol. The ISAKMP standard specifies a "Payload Length" field within the "Generic Payload Header". This field is populated by the sender and specifies the length in octets of the current payload, including the generic payload header. A flaw in the handling of packets with a specified length of zero could cause isakmpd to enter an infinite loop, preempting normal operations.

This issue is reportedly similar to VU#738518.


A remote attacker could cause the isakmpd service to become unresponsive. Subsequent IPsec-enabled communications may be disrupted as a result.


Apply a patch from the vendor

Patches have been released to address this issue. Please see the Systems Affected section of this document for more details.

Vendor Information


OpenBSD Affected

Updated:  August 20, 2004



Vendor Statement

Several bugs have been found in the ISAKMP daemon which can lead to memory
leaks and a remote denial of service condition. An attacker can craft
malformed payloads that can cause the isakmpd(8) process to stop
processing requests.

The problem is fixed in -current, 3.4-stable and 3.3-stable.

Patches are available at:

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

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This vulnerability was discovered by Rapid7 using their Striker test suite.

This document was written by Chad R Dougherty based on information published in Rapid7 Advisory R7-0018.

Other Information

CVE IDs: CVE-2004-0218
Severity Metric: 1.69
Date Public: 2004-03-19
Date First Published: 2004-08-27
Date Last Updated: 2004-08-27 13:28 UTC
Document Revision: 11

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