[Full-Disclosure] [HV-HIGH] MS Word multiple exceptions, at least one exploitable
To: firstname.lastname@example.org, email@example.com Date: Wed, 6 Oct 2004 16:53:00 -0700
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MS Word multiple exceptions, at least one exploitable.
MS Word is a highly overrated and widely used text processor, a part of
monstrous collection of applications and de-facto platform for virus and
worm replication known as MS Office suite.
All tests were performed using MS Word 2002 (10.6612.6714) SP3 with all
the latest patches installed.
Cause and Effect:
Sufficient data validation is not performed when winword.exe parses the
document file. As a result, it is possible to trigger an exception by
modifying data within *.doc file.
There are two exception types, one is triggered when winword.exe
tries to read from invalid memory region using offset value taken from the
document file. This exception is not exploitable.
The second exception is more interesting and most likely exploitable.
It is triggered by signed word->dword expansion that is later placed in
ECX, shifted right twice, and used as counter value for MOVSD instruction.
I.e. winword.exe code tried to copy nearly 4GB of RAM.
Below is a fragment of an empty *.doc file. Note the sequence of 0xAA characters
on line #3. When MS Word parsed this part of file, an exceptions occurs.
It is possible to trigger two other "access violation" conditions by modifying
data represented on lines #2 and #3.
00001400: 14 00 0F 00 12 00 01 00 9C 00 0F 00 03 00 00 00 ................
00001410: 00 00 00 00 00 00 40 00 00 40 F1 FF 02 00 40 00 ................
00001420: AA AA AA AA AA AA AA AA AA AA AA AA 4E 00 6F 00 ............N.o.
00001430: 72 00 6D 00 61 00 6C 00 00 00 02 00 00 00 18 00 r.m.a.l.........
At the time of release vendor was not aware of the vulnerability.
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