This module exploits a memory corruption vulnerability within Microsoft's
HTML engine (mshtml). When parsing an HTML page containing a specially
crafted CSS tag, memory corruption occurs that can lead arbitrary code
It seems like Microsoft code inadvertently increments a vtable pointer to
point to an unaligned address within the vtable's function pointers. This
leads to the program counter being set to the address determined by the
address "[vtable+0x30+1]". The particular address depends on the exact
version of the mshtml library in use.
Since the address depends on the version of mshtml, some versions may not
be exploitable. Specifically, those ending up with a program counter value
within another module, in kernel space, or just not able to be reached with
various memory spraying techniques.
Also, since the address is not controllable, it is unlikely to be possible
to use ROP to bypass non-executable memory protections.
- Matteo Memelli
- jduck <email@example.com>