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Cisco IOS IPv6 denial-of-service vulnerability

Vulnerability Note VU#472582

Original Release Date: 2005-01-26 | Last Revised: 2005-02-01


A vulnerability in the way Cisco IOS handles IPv6 packets could result in a remotely exploitable denial of service.


The Cisco Internetwork Operating System (IOS) includes support for processing Internet Protocol version 6 (IPv6) packets. A vulnerability in the way that IOS handles a sequence of specially crafted IPv6 packets could cause an affected device to reload (reboot), resulting in a denial of service. The specific nature of the crafted packets exploiting this vulnerability is not known. Only devices running IOS that have IPv6-configured interfaces, either physical or logical (e.g., tunnels), are vulnerable to this issue.


A remote attacker may be able to cause an affected device to reload, thereby creating a denial of service condition.



Cisco has addressed this issue in new versions of the IOS software. Please see Cisco's Security Advisory for more details.

Vendor Information


Cisco Systems Inc. Affected

Updated:  January 26, 2005



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

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


Cisco has published Cisco Security Advisory cisco-sa-20050126-ipv6 in response to this issue. Affected users are strongly encouraged to review this advisory and upgrade to a version of the IOS software that contains a fix.

Users who are unable to install the upgraded software should consider implementing the workarounds described in the Cisco advisory.

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

CVSS Metrics

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Thanks to Cisco PSIRT for reporting this vulnerability.

This document was written by Chad R Dougherty.

Other Information

CVE IDs: None
Severity Metric: 10.61
Date Public: 2005-01-26
Date First Published: 2005-01-26
Date Last Updated: 2005-02-01 20:50 UTC
Document Revision: 11

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