Detailed Exploit Published for Critical Windows Flaw

In an unusual move, Microsoft has released a formal security advisory to warn of the publication of "detailed exploit code" that targets a critical Windows vulnerability.

The software makers security response unit is strongly urging Windows users—especially businesses running Windows 2000—to patch the vulnerabilities addressed in the MS06-025 bulletin because of the potential for a worm attack.

The MS06-025 bulletin provides fixes for a pair of code execution flaws in the RRAS (Routing and Remote Access Service) in Windows. On Windows 2000 systems, the flaws carry a "critical" rating because it presents a remote unauthenticated attack vector.

Both flaws could allow a remote attacker to take "complete control" of an affected system and because a blow-by-blow exploit has been published on the Web, Microsoft is bracing for the possibility of a disruptive attack similar to the Zotob worm that hit several high-provide targets in August 2005.

The exploit code was released by security consultant HD Moore as part of the Metasploit Framework, an open-source tool for penetration testing and exploit development.

"When something like this happens so quickly after release we wanted to highlight that fact, and let you know that were not currently aware of any active attacks utilizing this exploit code at this time," said Microsoft security program manager Stephen Toulouse.

"We have confirmed that the exploit code does not affect users who have installed the update detailed in MS06-025 on their computers. So we continue to recommend that customers apply the that update," Toulouse added.

As is customary, Microsofts advisory included a knock against "certain security researchers" for breaching what it described as "commonly accepted industry practice" with the publication of published exploit code that puts computer users at risk.

"We continue to urge security researchers to disclose vulnerability information responsibly and allow customers time to deploy updates so they do not aid criminals in their attempt to take advantage of software vulnerabilities," the company said.

In an entry on the Metasploit blog, HD Moore lashed back, arguing that the so-called accepted industry practice on responsible disclosure does not exist.

"Verisign pays for exclusive rights to new vulnerabilities and sells a limited version of this data to their subscribers. Digital Armaments pays for exclusive rights to new vulnerabilities and then shares the data with its members. Immunity sells access to exploits and vulnerability information, often before the vendor is notified," Moore said, referring to third-party vendors that have made a business out of purchasing the rights of zero-day vulnerabilities.

Moore also pointed out that the exploit was released on June 22, a full nine days after Microsofts June 13 Patch Day. "This nine-day period is a significant delay in the security world…Even dial-up users can complete an automated update in nine days," he added.

Interestingly, Moore claims that the exploit actually targets a different bug than the one mentioned in Microsofts bulletin. He said the exploit code pertains to a flaw that was silently patched and not documented by Microsoft.

"This is a common occurrence with proprietary software vendors, since the process of looking for one bug often turns up a dozen more that were never mentioned in any public documents.

"Microsoft never mentioned this specific vulnerability in the advisory or to the Microsoft 0-Day Club (Microsoft Security Support Alliance), which meant that no intrusion detection systems were able to detect the Metasploit module," Moore said.

Microsofts practice of silently fixing bugs without proper disclosure has been roundly criticized by security researchers.

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