"We found the problem last October and notified Microsoft," said Gerhard Eschelbeck, chief technical officer at Qualys.

"The problem is that the standard is not particularly clear in how to deal with this, and different vendors have different solutions. Most of the vendors affected have released patches or will release patches in the coming days."

The three other patches, which affect Windows, are rated 'important' by Microsoft, and could allow remote control of PCs if used correctly. Microsoft has been working for the last three years to improve the security and reliability of its software under its Trustworthy Computing initiative, as more and more malicious software targets weaknesses in Windows and other Microsoft software reports Reuters