A former Microsoft worker has identified security vulnerabilities in smart card plug-in software for Windows Vista that might allow hackers to take over vulnerable PCs.

Dan Griffin used a fuzzing tool he developed, dubbed SCardFuzz, to find bugs in software from an unnamed smart card vendor. Griffin, who left Redmond's smart card development team to work for small Seattle-based security consultancy JW Secure, plans to demo the hack (which he claims might allow attackers to gain full system access) at the CanSecWest security conference in Vancouver at the end of March.

The SCardFuzz tool creates an applet on smart cards that generates a stream of fake and jumbled data. This malformed data is used to probe Microsoft's Smart Card Minidriver interface for problems.

SCardFuzz creates a heap-based buffer overflow in the unnamed vendor’s plug-in for Microsoft Vista, allowing hackers to crash or take control of vulnerable PCs. "You insert it into a reader on an unattended machine ... And you can take out a system process and at best, make it crash, or at worst, take over that process and control it," Griffin explained.

The same attack methodology ought to work under Windows XP, Heise security reports. ®

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