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Cisco IPS fails to properly check fragmented IP packets

Vulnerability Note VU#658884

Original Release Date: 2006-09-20 | Last Revised: 2006-09-20


Cisco IPS systems may fail to check specially-crafted IP packets that are fragmented.


Some Cisco intrusion prevention system (IPS) products can be configured as passive intrusion detection systems (IDS) or active IPS systems. Cisco refers to the IPS mode as "inline" and the IDS mode as "promiscuous".

An attacker may be able to create a stream of specially crafted fragmented IP packets that are not processed by the IPS. This would allow an attacker to generate malicious traffic that evades IPS inspection.


IPS products in inline mode may allow malicious traffic to pass through them. IPS products in promiscuous mode may not detect malicious traffic.


Cisco has released an update that addresses this issue. See Cisco Security Advisory cisco-sa-20060920-ips for more details.

Vendor Information

Affected   Unknown   Unaffected

Cisco Systems, Inc.

Updated:  September 20, 2006



Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

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


See for more details.

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CVSS Metrics

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



Cisco credits Pratap Ramamurthy and Shai Rubin for reporting this vulnerability.

This document was written by Ryan Giobbi.

Other Information

CVE IDs: None
Severity Metric: 4.59
Date Public: 2006-09-20
Date First Published: 2006-09-20
Date Last Updated: 2006-09-20 19:11 UTC
Document Revision: 16

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