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Microsoft Windows URI Handling Command Execution Vulnerability
Secunia Advisory: SA26201
Release Date: 2007-07-26
Last Update: 2007-11-13
Popularity: 56,228 views

Critical:
Highly critical
Impact: System access
Where: From remote
Solution Status: Vendor Patch

OS:Microsoft Windows Server 2003 Datacenter Edition
Microsoft Windows Server 2003 Enterprise Edition
Microsoft Windows Server 2003 Standard Edition
Microsoft Windows Server 2003 Web Edition
Microsoft Windows XP Home Edition
Microsoft Windows XP Professional

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CVE reference:CVE-2007-3896
CVE-2007-4041
CVE-2007-5020


Description:
A vulnerability has been discovered in Microsoft Windows, which can be exploited by malicious people to compromise a vulnerable system.

The vulnerability is caused due to an input validation error within the Windows shell (shell32.dll) when handling specially crafted URIs with registered URI handlers (e.g. "mailto", "news", "nntp", "snews", "telnet", and "http"). This can be exploited to execute arbitrary commands when a user of certain applications (e.g. Firefox) visits a malicious website or clicks on a link with a specially crafted URI containing a "%" character and ending with a certain extension (e.g. ".bat" or ".cmd").

Examples:
mailto:test%../../../../windows/system32/calc.exe".cmd
nntp:../../../../../Windows/system32/telnet.exe" "secunia.com 80%.bat

Successful exploitation using currently known vectors requires that Internet Explorer 7 is installed on the system, though the core problem exists on Windows system with other versions of Internet Explorer as well.

The following applications have been identified as attack vectors on a fully patched Windows XP SP2 and Windows Server 2003 SP2 system:
* Firefox version 2.0.0.5
* Netscape Navigator version 9.0b2
* mIRC version 6.3
* Adobe Reader/Acrobat version 8.1 and prior (when opening PDF files)
* Outlook Express 6 (e.g. when following specially crafted links in VCards)
* Outlook 2000 (e.g. when following specially crafted links in VCards)

Other versions and applications may also be affected.

Solution:
Apply patches.

Windows XP SP2:
http://www.microsoft.com/downloads/de...=8ba1c2f9-1bde-4e97-b327-21259c5e5104

Windows XP Professional x64 Edition (optionally with SP2):
http://www.microsoft.com/downloads/de...=4ef7fdd7-8887-4c64-a70c-c6ae734d7c5f

Windows Server 2003 SP1/SP2:
http://www.microsoft.com/downloads/de...=e5d8a866-2c1f-4035-8325-c1be61a75c3b

Windows Server 2003 x64 Edition (optionally with SP2):
http://www.microsoft.com/downloads/de...=bf26da08-15b8-4d65-ba12-4cc74c7a1326

Windows Server 2003 with SP1/SP2 for Itanium-based systems:
http://www.microsoft.com/downloads/de...=1c055f11-3273-4a4c-a33f-bf61ac9ec4c5

Provided and/or discovered by:
Reported as a Firefox browser vulnerability by:
* Billy (BK) Rios
* Nathan McFeters, Ernst & Young's Advanced Security Center

Firefox not escaping quotes originally discussed by:
* Jesper Johansson

Identification of core Windows problem and additional research by Secunia Research.

Changelog:
2007-07-27: Updated credits.
2007-07-30: Added link to US-CERT.
2007-08-01: Added CVE reference.
2007-10-04: Changed the statement "Other versions and browsers..." to "Other versions and applications.." to state that browsers are not the only vectors.
2007-10-08: Updated advisory and "Solution" section to include Adobe Reader/Acrobat as another vector. Added additional CVE reference.
2007-10-09: Updated "Description" section and credits. Added "Outlook 2000" and "Outlook Express 6" as attack vectors when e.g. handling VCards based on additional research by Carsten Eiram, Secunia Research. Outlook/Outlook Express also independently mentioned as attack vectors by Brett Moore.
2007-10-11: Update "Original Advisory" section with links to Microsoft. Added additional CVE reference.
2007-10-23: Added additional link to Adobe in "Other References" section.
2007-10-24: Updated "Extended Solution" section.
2007-11-13: Updated "Solution" section.

Original Advisory:
Microsoft (KB943521):
http://www.microsoft.com/technet/security/advisory/943521.mspx
http://blogs.technet.com/msrc/archive...ound-on-security-advisory-943521.aspx

Billy (BK) Rios:
http://xs-sniper.com/blog/2007/07/24/remote-command-execution-in-firefox-2005/

Other References:
MS07-061 (KB943460):
http://www.microsoft.com/technet/security/Bulletin/MS07-061.mspx

US-CERT VU#783400:
http://www.kb.cert.org/vuls/id/783400

US-CERT VU#403150:
http://www.kb.cert.org/vuls/id/403150

Jesper Johansson blog:
http://msinfluentials.com/blogs/jespe...la-quotes-are-not-legal-in-a-url.aspx

Adobe:
http://www.adobe.com/support/security/advisories/apsa07-04.html
http://www.adobe.com/support/security/bulletins/apsb07-18.html

Extended Solution:
The "Extended Solution" section is available for Secunia customers only. Request a trial and get access to the Secunia Customer Area and Extended Secunia advisories.


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