MS13-090 CardSpaceClaimCollection ActiveX Integer Underflow

This module exploits a vulnerability on the CardSpaceClaimCollection class from the
icardie.dll ActiveX control. The vulnerability exists while the handling of the
CardSpaceClaimCollection object. CardSpaceClaimCollections stores a collection of
elements on a SafeArray and keeps a size field, counting the number of elements on the
collection. By calling the remove() method on an empty CardSpaceClaimCollection it is
possible to underflow the length field, storing a negative integer. Later, a call to
the add() method will use the corrupted length field to compute the address where write
into the SafeArray data, allowing to corrupt memory with a pointer to controlled contents.
This module achieves code execution by using VBScript as discovered in the wild on
November 2013 to (1) create an array of html OBJECT elements, (2) create holes, (3) create
a CardSpaceClaimCollection whose SafeArray data will reuse one of the holes, (4) corrupt
one of the legit OBJECT elements with the described integer overflow and (5) achieve code
execution by forcing the use of the corrupted OBJECT.

Unknown
juan vazquez [email protected]

Windows