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Vulnerability in Mulitple Microsoft Products for Mac OS

Posted on April 9, 2002

Fixes

To fix Internet Explorer:

This is done by updating through the Software Update Pane/Control Panel.
Patch Microsoft Office Products: Patch is Here
More Information:Security Alert

Vulnerability: Run code attacker wants.
Severity Level: Microsoft suggests Critical
Affected Software:

  •     Microsoft Internet Explorer 5.1 for Macintosh OS X
  •     Microsoft Internet Explorer 5.1 for Macintosh OS 8 & 9
  •     Microsoft Outlook Express 5.0.-5.0.3 for Macintosh
  •     Microsoft Entourage v. X for Macintosh
  •     Microsoft Entourage 2001 for Macintosh
  •     Microsoft PowerPoint v. X for Macintosh
  •     Microsoft PowerPoint 2001 for Macintosh
  •     Microsoft PowerPoint 98 for Macintosh
  •     Microsoft Excel v. X for Macintosh
  •     Microsoft Excel 2001 for Macintosh

Josha Bronson of AngryPacket Security and w00w00 compiled the advisory below which, microsoft did release a patch for their products and should be downloaded now.

w00w00 (http://www.w00w00.org)
Angry Packet Security (http://sec.angrypacket.com)

Vulnerability in Multiple Microsoft Products for Mac OS

HTML format: http://www.w00w00.org/advisories/ms_macos.html
Text format: http://www.w00w00.org/files/advisories/ms_macos.txt

SOFTWARE VERSIONS AFFECTED

  • Microsoft Internet Explorer
    Versions affected: 5.1
    Platforms affected: Mac OS 8, 9, and X
  • Microsoft Outlook Express
    Versions affected: 5.0.2
    Platforms affected: all Mac OS
  • Microsft Entourage
    Versions affected: 2001 and X
    Platforms affected: all Mac OS
  • Microsoft PowerPoint
    Versions affected: 98, 2001, and X
    Platforms affected: all Mac OS
  • Microsoft Excel
    Versions affected: 2001 and X
    Platforms affected: all Mac OS
  • Microsoft Word
    Versions affected: 2001
    Platforms affected: all Mac OS

PRELUDE

A bug in Internet Explorer for Mac OS X was originally reported to Microsoft by Josha Bronson of Angry Packet Security on January 4, 2002.

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.

DESCRIPTION

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.

IMPLICATIONS

In most cases, the user would need to click on the link to be attacked. In the case of Entourage or Outlook Express, however, just opening the email will cause this. This leaves the potential for a worm. The magnitude depends on how many people actually use Entourage and Outlook Express for Mac OS. In all cases, writing shellcode to exploit this problem is simple. 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.

EXPLOIT

The following HTML file will demonstrate the problem. We chose to use IMG simply because that is instantly loaded, but an <A HREF=…> could have been used also. It can also be viewed (in live form) at http://www.w00w00.org/files/advisories/ie_sample.html.  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.

<html>
<body>
<img src=file:///[1313 characters]%41%42%43%44>
</body>
</html>

PATCHES

For Internet Explorer, a patch is available from:
http://www.apple.com/macosx/upgrade/softwareupdates.html.

For the other products, the patches can be downloaded from:
http://www.microsoft.com/mac/download.

CREDIT

w00w00 would like to thank Angry Packet for involving us in their efforts to get Microsoft to resolve this problem after their attempts failed.

UPDATES

To fix Internet Explorer visit your Software Update Control Panel and update. for the Microsoft Office Product update visit the update page.

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