Vulnerability Note VU#201984

Cisco IOS fails to properly handle Next Hop Resolution Protocol packets

Overview

Cisco IOS fails to properly handle Next Hop Resolution Protocol packets, which could allow a remote, unauthenticated attacker to execute arbitrary code or cause a denial of service.

I. Description

Cisco IOS is an operating system that is used on Cisco network devices. Cisco IOS supports a feature called Next Hop Resolution Protocol (NHRP). NHRP is a component of the Dynamic Multipoint Virtual Private Network (DMVPN) feature. NHRP is not enabled by default in Cisco IOS. Cisco IOS fails to properly handle NHRP packets. According to the Cisco Security Advisory,

NHRP can operate in three ways: at the link layer (Layer 2), over Generic Routing Encapsulation (GRE) and multipoint GRE (mGRE) tunnels and directly on IP (IP protocol number 54). This vulnerability affects all three methods of operation.

Note that exploit code for this vulnerability is publicly available.

II. Impact

A remote, unauthenticated attacker may be able to execute arbitrary code or cause a denial of service on an affected device.

III. Solution

Apply an update

This issue is addressed in Cisco Security Advisory cisco-sa-20070808-nhrp.

Workarounds

Cisco Security Advisory cisco-sa-20070808-nhrp offers several workarounds, including infrastructure ACLs and Control Plane Policing.

Systems Affected

Vendor	Status	Date Updated
Cisco Systems, Inc.	Vulnerable	9-Aug-2007

References

http://www.cisco.com/warp/public/707/cisco-sa-20070808-nhrp.shtml
http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a0080435815.html
http://secunia.com/advisories/26360/

Credit

Thanks to Cisco for reporting this vulnerability, who in turn credit Martin Kluge.

This document was written by Will Dormann.

Other Information

Date Public	08/08/2007
Date First Published	08/09/2007 02:10:26 PM
Date Last Updated	08/10/2007
CERT Advisory
CVE Name
Metric	17.85
Document Revision	4