Microsoft Posts Fix For SMB Vulnerability

Microsoft on Tuesday posted a fix for a zero-day vulnerability in its Sever Message Block (SMB) software, a flaw that has been publicly known for about three weeks.

Microsoft posted a Security Advisory about the issue on September 8, the same day it released five Security Bulletins addressing other software vulnerabilities. The SMB vulnerability could allow an attacker to execute malicious code or conduct a denial of service attack.

The fix consists of a clickable link that will disable SMB v2. A link to re-enable it is also provided.

Microsoft is likely to issue a full patch during its October patch cycle. It may also address two other zero-day vulnerabilities in its IIS software that were made public at the beginning of the month.

Microsoft claims that the SMB vulnerability "was not responsibly disclosed," meaning the exploit code was published without sufficient prior notification to the company.

Laurent Graffie, who posted exploit code for the SMB2 vulnerability on September 7, acknowledges that his note to Microsoft may have gone astray -- he sent it to "microssoft.com" by mistake --but maintains that Microsoft knew about the flaw.

In comments posted with his exploit code, he points to a Microsoft spokeperson's comments in an article in Technology Review as evidence that the company was aware of the vulnerability at least as early as July.

According to the Microsoft spokesperson quoted in the article, Microsoft identified the vulnerability independently and fixed it in Windows 7 RTM (release to manufacturer) and Windows Server 2008 R2, which were released on July 22.

Graffie contends that "this specific bug (my payload) was introduced by a security patch (MS07-063)," a fix for another SMB vulnerability that was released in December 2007.

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