The patch, which fixes the way Windows parses shortcut icons, will be released on Monday at around 10 a.m. California time. It comes two weeks after reports surfaced that unknown hackers were exploiting the flaw in an attempt to install malware on systems that control the operations of power plants and other critical infrastructure. At least two customer of SCADA, or supervisory control and data acquisition, software offered by Siemens have been hit by a computer worm that exploits the bug.
“We are releasing the bulletin as we’ve completed the required testing and the update has achieved the appropriate quality bar for broad distribution to customers,” Christopher Budd, Microsoft’s senior security response communications manager,” wrote. “Additionally, we’re able to confirm that, in the past few days, we’ve seen an increase in attempts to exploit the vulnerability. We firmly believe that releasing the update out of band is the best thing to do to help protect our customers.”
The vulnerability resides in the Windows LNK extension, which is used to create shortcuts on the operating system desktop or in select folders to make it easier to access files. The OS fails to adequately parse some parameters, making it possible to embed malicious code that is automatically executed when an icon is viewed. Hackers have been exploiting the flaw using worms that spread over USB drives. Microsoft has also warned that it is exploitable using local network file-sharing features or the WebDAV, or Web Distributed Authoring and Versioning, client service.
It affects every supported version of Windows.
Until the patch is released, the only way for users to protect themselves is to deploy a workaround that prevents folder icons from being displayed.
Microsoft rarely issues patches outside of its monthly schedule, which it put in place in 2003 so that customers in large organizations had time to make sure the changes don’t disrupt operations. By our count, this is the third time this year Microsoft has issued a so-called out-of-band update.