Or lack of currently available patch as the case may be. From the previous link it appears that there was at least one previously announced vulnerability that was not addressed in the recent patch day from Microsoft. From MS…
“this is a DoS only issue that was not addressed in MS06-040, but will be addressed in a bulletin.”
Not timeline yet on when… There are also public exploits out for (possibly related to MS06-046) which is related to the MS Help system.