Vulnerability Note VU#658884

Cisco IPS fails to properly check fragmented IP packets

Overview

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

I. Description

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.

II. Impact

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

III. Solution

Upgrade

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

Systems Affected

Vendor	Status	Date Notified	Date Updated
Cisco Systems, Inc.	Vulnerable	20-Sep-2006

References

http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml
http://www.cisco.com/en/US/products/hw/vpndevc/ps4077/products_qanda_item0900aecd801e6a99.shtml

Credit

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

This document was written by Ryan Giobbi.

Other Information

Date Public:	2006-09-20
Date First Published:	2006-09-20
Date Last Updated:	2006-09-20
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	4.59
Document Revision:	16

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Produced 2006 by US-CERT, a government organization
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