There is a vulnerability in multiple Microsoft products on Mac OS.
The problem lies in the handling of a lengthy subdirectory in the
file:// directive, such as file:///AAAAAA[...] or
file://A/A/A/A/[...]. The number of subdirectories is trivial as
long as there is at least one.

Vulnerability in Multiple Microsoft Products for Mac OS
HTML format:
Text format:


Microsft Internet Explorer
Versions affected: 5.1
Platforms affected: Mac OS 8, 9, and X

Microsft Outlook Express
Versions affected: 5.0.2
Platforms affected: all Mac OS

Microsft Entourage
Versions affected: 2001 and X
Platforms affected: all Mac OS

Microsft PowerPoint
Versions affected: 98, 2001, and X
Platforms affected: all Mac OS

Microsft Excel
Versions affected: 2001 and X
Platforms affected: all Mac OS

Microsft Word
Versions affected: 2001
Platforms affected: all Mac OS


A bug in Internet Explorer for Mac OS X was originally reported to
Microsoft by Josha Bronson of Angry Packet Security on January 4,

Due to some internal mishandling at Microsoft, this was brushed off
until w00w00 informed Microsoft of its intention to release the
information on February 17. We originally gave them a deadline of
two weeks until we discovered that this affected Entourage (the
Outlook-equivalent for Mac OS). When Microsoft determined this
affected most of their Office suite on Mac OS, we felt it was
appropriate to give them time to fix it.


This is another vulnerability with potentially far reaching
consequences. In the case of Entourage, it has the potential for a
worm, with the magnitude depending on how many people actually use
Entourage (Microsoft's Outlook equivalent for Mac OS). In all cases,
writing shellcode to exploit this problem is simply--much more
simple than shellcode for the AOL Instant Messenger problem we
reported in January. Given that Mac OS X has a Unix interface,
existing PowerPC shellcode that runs /bin/sh will work. No complex
shellcode is needed to bind to a port or download an application off
the web. The /bin/sh shellcode would need to be changed from an
interactive shell to one that will execute a chain of commands.
There are enough commands on Mac OS by default to allow an attacker
to download and execute an application off of a web page. The
downloaded application could do any number of things, such as read
off the user's contact list and send the same email to exploit to
all of the user's contacts.


The following HTML file will demonstrate the problem. We chose to
use IMG simply because that is instantly loaded, but an
could have been used also. It can also be viewed (in
live form) at
It overwrites the saved link register which is used for a
subroutine's return address on PowerPC. This will allow remote
execution of arbitrary code. The saved link register is overwritten
by the 0x41424344. This vulnerability will allow up to 1313
characters before the saved link register. Pure binary data
(including NUL bytes) can be used by escaping it (i.e., A as %41).
However, using "%41" will count as three characters, rather than
just one. Note: by character I mean unibyte characters.


For Internet Explorer, a patch is available from For
the other products, the patches can be downloaded from