A security researcher has said there is a zero-day vulnerability affecting Windows 7 and Vista.
The flaw in Windows 7 could allow an attack which would cause a critical system error, or "Blue Screen of Death", according to researcher Laurent Gaffie.
Gaffie wrote in his blog that the flaw lies in a Server Message Block 2 (SMB2) driver.
"SRV2.SYS fails to handle malformed SMB headers for the NEGOTIATE PROTOCOL REQUEST functionality," wrote Gaffie in a blog post on Monday.
Gaffie said he had contacted Microsoft. Comments on his blog by other users said that the flaw could lead not only to denial of service, but could also lead to remote code execution.
Computer security publication 'The H' wrote on Tuesday that its German sister publication had tested the proof-of-concept code, and that while the exploit had caused a reboot on Vista, the exploit had not worked on Windows 7.
Metasploit creator HD Moore said in a tweet on Tuesday that an SMB bug appeared to have been introduced into Vista SP1. Coder Josh Goebel said in a blog post that he had added the exploit code to Metasploit.
Microsoft had not responded to a request for comment at the time of writing.
This article was originally posted on ZDNet UK.