Researchers Discredit Microsoft’s Bug Claim

By Dave Nixon

A security researcher has dismissed Microsoft’s assertion that the year’s first critical Windows vulnerability would be “difficult and unlikely” to be exploited by attackers.

On Tuesday, in relation to the TCP/IP flaw spelled out 8 January in Microsoft’s MS08-001 security bulletin, Immunity updated an operational exploit, and published a Flash demonstration of the attack on its website.

The exploit, unavailable to the public, was released to customers of its CANVAS penetration testing software and was a revised version of code first issued two weeks ago.

In a message to his Dailydave security mailing list, “This demonstrates conclusively that the MS08-001 IGMPv3 vulnerability is highly exploitable,” said Dave Aitel, Immunity’s chief technology officer.

Aitel’s claim disputed Microsoft’s earlier assessment that “there are a number of factors that make exploitation of this issue difficult and unlikely in real-world conditions.”

However, Immunity did recognize that its most recent exploit was not 100 percent consistent.

Other security companies responded to the overhauled attack code and Flash proof by issuing new alerts. For example, Symantec, sent a new advice to customers of its DeepSight threat network. “The exploit demonstrates remote code execution. The exploit works against Windows XP SP2 English Default and shows two Windows XP SP2 computers on a local subnet with firewall enabled being compromised.”, noted Symantec.

It advocated that users who have not previously deployed the patches Microsoft issued 8 January to do so without delay.

Previously, in a detailed analysis of the flaw and its exploitation, Aitel had called out the IGMP (Internet Group Management Protocol) vulnerability as a potential blockbuster for 2008 and Symantec agreed that the incentive to hackers would be great even if replicating Immunity’s work might be difficult.

“Although exploitation of a remote kernel flaw is considered quite difficult, over the past few years numerous papers have been released on the subject,” the Symantec analysis noted. “Examples of exploits successfully leveraging such flaws have also been released to the public. Therefore, we assume that this issue will be exploited in the wild to execute arbitrary code. Deploy patches immediately.”

Triumphant attacks by the Immunity exploit, and any other comparable exploits, permits arbitrary code to execute within the context of the Windows kernel, said Symantec, an especially intolerable scenario for Windows Vista.

“This is especially critical on Vista, due to its enhanced kernel security mechanisms,” said Symantec. “A local user, even an admin, may have difficultly introducing unsigned code into the kernel, but in this case, it can be done remotely without any authentication whatsoever. “

“This vulnerability presents an opportunity to not only execute arbitrary code on the system, but also to install backdoors and other malicious tools as well as a rootkit, which may normally be more difficult with a typical remote userland vulnerability.”

In its 8 January MS08-001 bulletin, Microsoft categorised the IGMP flaw as “Critical” for Windows XP SP2, Windows Vista, Windows Small Business Server and Windows Home Server. On other versions, including Windows Server 2003, the bug rated an “Important” label.