Security researchers claim that a new zero-day vulnerability affecting Windows 7 and Vista could cause a critical system error and allow for remote code execution.

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 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. Microsoft said in a statement on Tuesday that it was investigating, but said it is "currently unaware of any attacks trying to use the claimed vulnerability or of customer impact."

Update: According to this security advisory, reports of a zero-day flaw that supposedly affected Windows 7 are not true. The final version of Microsoft's latest OS is not vulnerable to the attacks, everyone can calm down.