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Home » Hacking News » Cisco SNMP Read-Write ILMI Community String Vulnerability

Cisco SNMP Read-Write ILMI Community String Vulnerability

by Phiber on February 28th, 2001 Cisco IOS software releases based on versions 11.x and 12.0 contain a defect that allows a limited number of SNMP objects to be viewed and modified without authorization using a undocumented ILMI community string. Some of the modifiable objects are confined to the MIB-II system group, such as "sysContact", "sysLocation", and "sysName", that do not affect the device's normal operation but that may cause confusion if modified unexpectedly. The remaining objects are contained in the LAN-EMULATION-CLIENT and PNNI MIBs, and modification of those objects may affect ATM configuration. An affected device might be vulnerable to a denial-of-service attack if it is not protected against unauthorized use of the ILMI community string.

The vulnerability is only present in certain combinations of IOS
releases on Cisco routers and switches. ILMI is a necessary
component for ATM, and the vulnerability is present in every IOS
release that contains the supporting software for ATM and ILMI
without regard to the actual presence of an ATM interface or the
physical ability of the device to support an ATM connection.

To remove this vulnerability, Cisco is offering free software
upgrades for all affected platforms. The defect is documented in
DDTS record CSCdp11863.

A workaround can be applied to
certain IOS releases by disabling the ILMI community or "*ilmi" view
and applying an access list to prevent unauthorized access to SNMP.
Any affected system, regardless of software release, may be
protected by filtering SNMP traffic at a network perimeter or on
individual devices.

Download this advisory

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