Yet Another Buffer Overflow Bug.
A buffer overflow bug overwrites executable code or call stack saved registers, that will be executed or restored innocently at a later time.
This flaw seems to have an added, intentional, CALL instruction, into metadata in a file that should not have any executable instructions.
Very different. No flawed buffer arithmetic. Not the faking out of a legitimate call or jump with bad data, but the intentional call into a place that no one would have expect to have machine instructions.
Gibson has stated that the WMF vulnerability is not a buffer overflow bug.