Tavis Ormandy, s security researcher at Google, has found a new vulnerability in Windows that resides in a feature known as the Virtual DOS Machine. Ormandy says the bug was introduced in 1993 with Windows NT and that it exists in all 32-bit versions of Microsoft's operating systems released since 1993.
Attackers can use the vulnerability to make changes to parts of the operating system that are otherwise considered highly trusted and sensitive. Users are advises to turn off the MSDOS and WOWEXEC subsystems until Microsoft issues an update.
The vulnerability exists in all 32-bit versions of Microsoft OSes released since 1993, and proof-of-concept code works on the XP, Server 2003, Vista, Server 2008, and 7 versions of Windows, Ormandy reported. Presumably, Windows 2000 is also susceptible. Immunity, a Miami-based company that makes auditing software for security professionals, has already added a module exploiting the vulnerability to its product called Canvas. The exploit has been tested on all versions of Windows except for 3.1.
Ormandy said the security hole can easily be closed by turning off the MSDOS and WOWEXEC subsystems. The changes generally don't interfere with most tasks since they disable rarely-used 16-bit applications. He said he informed Microsoft security employees of the vulnerability in June.