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                     Secunia Research 13/12/2005

Microsoft Internet Explorer Keyboard Shortcut Processing Vulnerability

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Table of Contents

Affected Software....................................................1
Severity.............................................................2
Description of Vulnerability.........................................3
Solution.............................................................4
Time Table...........................................................5
Credits..............................................................6
References...........................................................7
About Secunia........................................................8
Verification.........................................................9

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1) Affected Software

Microsoft Internet Explorer 6.0

Other versions may also be affected.

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2) Severity

Rating: Highly critical
Impact: System access and security bypass
Where:  From remote

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3) Description of Vulnerability

Secunia Research has discovered a vulnerability in 
Microsoft Internet Explorer, which can be exploited by malicious 
people to trick users into executing malicious files.

The vulnerability is caused due to a design error in the processing 
of keyboard shortcuts for certain security dialogs. This can e.g. be 
exploited to delay the file download dialog and trick users into 
executing a malicious ".bat" file after pressing the "r" key.

A successful attack may be outlined as:
1. Detect that the user is typing on the keyboard.
2. Redirect to a malicious ".bat" file.
3. In a new thread, force the browser to consume a large amount of 
   CPU resources via a simple loop statement. This causes the 
   upcoming file download dialog to be delayed.
4. The user eventually presses the "r" key which is a keyboard 
   shortcut for opening the downloaded file. The download dialog has 
   not yet been shown for the user when this event occurs.
5. The loop statement stops causing the download dialog to be visible
   and the keyboard shortcut event is processed.
6. The malicious ".bat" file is launched.

The vulnerability has been confirmed on a fully patched system with 
Internet Explorer 6.0 and Microsoft Windows XP SP2. Other versions 
may also be affected.

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4) Solution

Apply patches.

Please see MS05-054 (KB905915):
http://www.microsoft.com/technet/security/Bulletin/MS05-054.mspx

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5) Time Table

21/05/2005 - Vulnerability discovered.
24/05/2005 - Vendor notified.
20/06/2005 - Vendor confirms the vulnerability.
13/12/2005 - Vendor issues patch.
13/12/2005 - Public disclosure.

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6) Credits

Discovered by Andreas Sandblad, Secunia Research.

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7) References

The Common Vulnerabilities and Exposures (CVE) project has assigned 
candidate number CAN-2005-2829 for the vulnerability.

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8) About Secunia

Secunia collects, validates, assesses, and writes advisories regarding
all the latest software vulnerabilities disclosed to the public. These
advisories are gathered in a publicly available database at the
Secunia web site:

http://secunia.com/

Secunia offers services to our customers enabling them to receive all
relevant vulnerability information to their specific system
configuration.

Secunia offers a FREE mailing list called Secunia Security Advisories:

http://secunia.com/secunia_security_advisories/

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9) Verification

Please verify this advisory by visiting the Secunia web site:
http://secunia.com/secunia_research/2005-7/advisory/

Complete list of vulnerability reports published by Secunia Research:
http://secunia.com/secunia_research/

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