Mozilla Firefox URL protocol handling vulnerability

Overview

Mozilla Firefox protocol handlers may allow remotely supplied JavaScript to execute with elevated privileges. This may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

Description

On Microsoft Windows systems, Mozilla Firefox installs protocol handlers for Mozilla-specific protocols, such as the FirefoxURL and FirefoxHTML protocols. If Microsoft Windows encounters a URL protocol it cannot handle natively it searches the Windows registry for the appropriate protocol handler. When the correct protocol handler is found, Windows passes it the URL string. By design Windows passes the URL string to the protocol handler as it was received without performing any sanitization.

Mozilla Firefox URL protocol handlers are constructed in a way that may allow a remote attacker to execute arbitrary JavaScript with elevated (chrome) privileges. Mozilla Firefox security restrictions detect and prevent the execution of such JavaScript. However, if a remote attacker can persuade a user with Firefox installed to access a specially crafted web page using Internet Explorer, and perhaps other Windows applications, the malicious JavaScript will be executed. Reports claim this vulnerability is introduced when Firefox versions 2.0.0.2 and later are installed.

Exploit code is publicly available for this vulnerability.

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Impact

This vulnerability may allow a remote, unauthenticated attacker to execute JavaScript with elevated (chrome) privileges. This essentially means that the attacker can execute arbitrary code with the privileges of the user.

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Solution

Update
Mozilla has addressed this vulnerability in Firefox 2.0.0.5.

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Unregister theFirefoxprotocols

Disabling the Mozilla Firefox protocol handlers will mitigate this vulnerability. To unregister the protocol handlers, delete or rename the following registry keys:

HKEY_CLASSES_ROOT\FirefoxURL
HKEY_CLASSES_ROOT\FirefoxHTML
Modifying the Windows registry may have unintended consequences and should be done with care.

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Vendor Information

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Mozilla __ Affected

Updated: July 18, 2007

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

Refer to <http://blog.mozilla.com/security/2007/07/10/security-issue-in-url-protocol-handling-on-windows/&gt;.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23358017 Feedback>).

Microsoft Corporation Unknown

Updated: July 10, 2007

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.virusbtn.com/news/virus_news/2007/07_11.xml&gt;
• <http://blog.mozilla.com/security/2007/07/10/security-issue-in-url-protocol-handling-on-windows/&gt;
• <http://secunia.com/advisories/25984/&gt;
• <http://www.securityfocus.com/bid/24837&gt;
• <http://www.frsirt.com/english/advisories/2007/2473&gt;
• <http://www.securitytracker.com/id?1018351&gt;
• <http://www.securitytracker.com/id?1018360&gt;
• <https://bugzilla.mozilla.org/show_bug.cgi?id=384384&gt;
• <http://www.mozilla.org/security/announce/2007/mfsa2007-23.html&gt;
• <http://wiki.mozilla.org/Firefox:2.0.0.5&gt;
• <http://secunia.com/advisories/26096/&gt;
• <http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=565&gt;

Acknowledgements

This vulnerability was publicly disclosed by Thor Larholm.

This document was written by Jeff Gennari.

Other Information

CVE IDs:	CVE-2007-3670
Severity Metric:	19.69 Date Public: