ShellExecuteFiasco — third-party patch for CVE-2007-3896

KJK::Hyperion <hackbunny@s0ftpj.org>

Download

File name: shellexecutefiasco.zip

Version: 1.1. Upgrade highly recommended.

Size: 16383 bytes

MD5 hash: 069eac48b2df43029a2a687e18a12505

SHA1 hash: 60305fecfbe749f274e44d9180c111640954341e

About

This is an unofficial, third-party patch for vulnerability CVE-2007-3896, intended to protect supported Microsoft operating systems until an official patch is released, and unsupported systems as well. You only need this patch if you have Internet Explorer 7 on any operating system older than Windows Vista, and only until Microsoft releases an official fix.

Attention third-party developers: stop being part of the problem and become part of the solution. Need to launch an URL in the default external application? Consider using my helper routines ShellExecuteURL and ShellExecuteURLEx (or at least read their code to understand what makes them work), instead of passing URLs directly to ShellExecute(Ex). It's a minimal amount of code and it adds no new dependencies to your program.

The present patch is dramatically under-tested and it has undergone no quality assurance procedure whatsoever, so please deploy with the greatest care. It has a very good chance of misbehaving and making your system unusable; should this happen, rebooting in safe mode with command prompt might make it possible to uninstall it, or it might as well not.

The patch consists of a ShellExecuteEx hook that prevents the execution of malformed URLs and enforces normalization of valid URLs. Programs registering custom URL schemes might not like, support or even know about normalized URLs: this patch will interfere with any such program to the point of unusability. The normalization proper is performed by Internet Explorer's low-level internet engine, which could mangle unknown URL schemes or otherwise act unpredictably when presented with abnormal input.

History

2007-10-17 — Version 1.1
2007-10-14 — Version 1.0

Installation

  1. Copy shellexecutefiasco.dll anywhere; %windir%\system32 will do.

  2. Run the command:

    1. regsvr32 full path to shellexecutefiasco.dll or regsvr32 /n /i:s full path to shellexecutefiasco.dll to install for all users

    2. regsvr32 /n /i:u full path to shellexecutefiasco.dll to install for the current user only.

  3. A message box will report whether the installation was successful.

You need to be a privileged user to install this patch.

Uninstallation

  1. Run the command regsvr32 /u full path to shellexecutefiasco.dll.

  2. A message box will report whether the uninstallation was successful.

  3. Delete shellexecutefiasco.dll, or rename it if it's in use. In the latter case, a logout will still be necessary to clear the patch from memory.

You need to be a privileged user to fully uninstall this patch.

Upgrade

  1. Uninstall the existing version.

  2. Install the new version.

License

The patch is released as open source under the following license:

Copyright (c) 2007 KJK::Hyperion

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.