Cisco vulnerability posted to Internet

Cisco vulnerability posted to Internet

One day after a security researcher and organizers of the Black Hat USA conference agreed not to post details of vulnerabilities in Cisco Systems's router software, the information has been published on the Internet.

On Friday, the Web site posted what appear to be slides written to accompany a presentation given by former Internet Security Systems (ISS) researcher Michael Lynn, at the Black Hat conference in Las Vegas. The slides had been published in conference materials for the show, but after a last-minute decision by ISS to cancel the presentation, they were literally ripped from the Black Hat books.

ISS had planned to replace the Wednesday presentation, entitled "The Holy Grail: Cisco IOS Shellcode and Remote Execution," with a different one, but Lynn, formerly a research analyst at ISS, quit his job and gave the Cisco presentation anyway.

In it, he described a now-patched flaw in the Internetwork Operating System (IOS) software used to power Cisco's routers, and demonstrated a buffer-overflow attack in which he took control of a router. Although Cisco was informed of the flaw by ISS, and patched its firmware in April, users running older versions of the company's software are at risk, he said.

Black Hat and Lynn were then sued by Cisco and ISS in an attempt to prevent the details of Lynn's talk from being circulated. On Thursday, the parties came to an agreement with Lynn agreeing to silence on the matter.

A number of the Cryptome slides appear to be nearly identical to Lynn's presentation, but unlike the slides that were presented at Black Hat, they contain the ISS logo, indicating that they may be copies of the original Black Hat show materials. They also do not include a link to Lynn's resume, which was on one of the last slides the newly unemployed researcher presented to the Black Hat audience.

The slides, which appeared to have been last modified on July 1, came from a source who asked not to be named, and who claimed that the document is "the Black Hat presentation," according to John Young, administrator of the Cryptome Web site. "The source was not Michael Lynn, or did not use that name," he said via e-mail.

A Cisco spokesman said his company is not planning any further legal action relating to Lynn's talk. "With the capabilities of the Internet, it becomes a futile effort," he said. "If you pop a down pillow in the middle of the street , you can't pick up all the feathers."

By Friday morning, the slides had also been posted on the Web site, and submitted to the Full Disclosure security mailing list.

Also on Friday, Cisco posted an advisory detailing Lynn's vulnerability, which research firm Secunia rated as "moderately critical."

The advisory says that products running certain versions of IOS are vulnerable to attack from specially written IPv6 (Internet Protocol version 6) packets. The attack must be launched from within a local area network and only affects devices that "have been explicitly configured to process IPv6," it says.

Cisco began fixing the vulnerability in its firmware last April, and so most customers who have up-to-date versions of IOS are not affected, the Cisco spokesman said. Some "non-mainstream" versions of Cisco's products may still be vulnerable to the attack, however, and Cisco is advising those users to turn off IPv6. "Of the small population that actually uses IPv6, there could be 10 percent that need to disable IPv6," he said.

Cisco expects that all versions of IOS will be patched soon, the spokesman said.

By suing Lynn and Black Hat, Cisco ended up drawing much more attention to the flaw than it would have otherwise received, according to Richard Forno, the independent security consultant who maintains the Web site. Forno said that he posted the slides, in part, to protest Cisco's heavy-handed handling of the matter. "When I found them, boom, up they went," he said. "I don't hold Cisco in high esteem right now for how they handled this."

The slides can be found at

Cisco's advisory can be found at

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