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CERT Coordination Center

Cisco IOS/CatOS exposes read-write SNMP community string via traversal of View-based Access Control MIB (VACM) using read-only community string

Vulnerability Note VU#645400

Original Release Date: 2001-05-01 | Last Revised: 2002-03-05


There is a vulnerability that permits unauthorized access to several switch and router products manufactured by Cisco Systems. An attacker who gains access to an affected device can read and modify its configuration, creating a denial-of-service condition, an information leak, or both.


Certain versions of the Cisco Internetworking Operating System (IOS) and Catalyst Operating System (CatOS) contain a default configuration that allows a read-only Simple Network Management Protocol (SNMP) community string to expose a read-write community string. The exposure occurs in the View-based Access Control (VACM) MIB, which is a Management Information Base module that allows system administrators to configure access policies for SNMP-managed devices. Once exposed, the read-write community string grants an attacker complete access to affected devices, allowing them to gather information, monitor network traffic, and alter or disrupt network operation.


This vulnerability allows attackers to read and modify any SNMP objects present on an affected device. Attackers exploiting this vulnerability can re-route or disrupt network traffic as well as gather information about network topology and system administration contacts.


Cisco has released an advisory that provides a list of affected products, along with instructions for obtaining fixed software. Because there are many possible combinations of hardware and software configurations, the CERT/CC recommends that all users of IOS and CatOS software consult the following Cisco Security Advisory:

Cisco has provided detailed information on implementing workarounds to address this issue. Please consult the Cisco advisory referenced above.

Vendor Information


Cisco Affected

Updated:  March 16, 2001



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.


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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The CERT/CC thanks Cisco Systems for providing a description of this vulnerability and a patch to address it.

This document was written by Jeffrey P. Lanza and is based on information obtained from a Cisco Security Advisory.

Other Information

CVE IDs: None
Severity Metric: 54.68
Date Public: 2001-02-28
Date First Published: 2001-05-01
Date Last Updated: 2002-03-05 22:52 UTC
Document Revision: 18

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