Ciscos IOS Open to Hackers

Company: Switch/router software holes let attackers control net devices, manipulate SSH sessions

Several serious vulnerabilities in Cisco Systems Inc.s Internetwork Operating System could catch unawares some enterprises that run the companys popular lines of routers and switches.

The networking company last week revealed several security holes that could allow attackers to gain control of devices running IOS or recover a secured session key.

The most serious vulnerability affects all versions of the San Jose, Calif., companys IOS software from Release 11.3 forward, which effectively encompasses all of Ciscos mainstream routers and switches.

When the HTTP server in IOS is enabled and local authorization is in use, an attacker could bypass the authentication function by sending a carefully crafted URL to the server. The attacker could then have complete control over the device and could see and change its configuration settings, Cisco officials acknowledged.

The vulnerability can be avoided by disabling the HTTP server feature.

Ciscos routers and switches are among the most widely deployed in the industry and make up a large portion of the Internets backbone. Because most Internet service providers and large network operators dont configure their routers to run HTTP, the scope of the vulnerability is somewhat smaller than it might have been.

But observers warn that Cisco switches come from the factory with the HTTP server enabled. Any user who does not disable that feature is at risk.

Cisco also said there are three vulnerabilities in the implementation of the Secure Shell protocol, known as SSH, included in all versions of IOS from 12.0 forward. The SSH flaw also affects versions 5.25 and 5.3.1 of Ciscos PIX (Private Internet Exchange) firewall software and Version 6.2 of the CatOS software running on some of the companys Catalyst switches.

All the SSH issues are known problems with the protocol itself but are considered serious.

A flaw in the integrity check process for the encrypted channels used in SSH could allow an attacker to insert arbitrary commands into the session after it has started. A second vulnerability could enable an attacker who intercepted the SSH packets to surmise the exact length of a users password. The third flaw could enable an attacker to recover the SSH session key if he or she were able to sniff the session.

There are no workarounds for the SSH vulnerabilities, but Cisco is making fixed software available for free.

"The SSH issue has been known, but its still serious," said David Crowe, director of network engineering for the Network for Education and Research in Oregon at the University of Oregon, in Eugene. "Its not just Ciscos problem, its a limitation of the version of the protocol. But you still have to be careful with it."