Citrix ICA Client ActiveX control buffer overflow

Overview

A vulnerability in an ActiveX control provided with the Citrix Presentation Server Client could allow a remote attacker to execute arbitrary code on an affected system.

Description

The Citrix Presentation Server Client software provides an ActiveX control that can be used to integrate the client into Web pages. The Citrix ICA Client ActiveX control, which is provided by Wfica.ocx, contains a buffer overflow vulnerability in the SendChannelData(``) method.

Citrix notes that his vulnerability is present in all versions of the Citrix Presentation Server Client for Windows earlier than 9.230.

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Impact

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), a remote, unauthenticated attacker may be able to execute arbitrary code with the privileges of the user. The attacker could also cause Internet Explorer (or the program using the WebBrowser control) to crash.

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Solution

Upgrade

Citrix has provided updated versions of the affected software to address this issue. Please see the corresponding Citrix Security Bulletin for more information.

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Disable the affected ActiveX control in Internet Explorer

The Citrix Presentation Server Client ActiveX control can be disabled in Internet Explorer by setting the kill bit for the following CLSID:

{238F6F83-B8B4-11CF-8771-00A024541EE3}
More information about how to set the kill bit is available in Microsoft Support Document 240797. Alternatively, the following text can be saved as a .REG file and imported to set the kill bit for this control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\``{238F6F83-B8B4-11CF-8771-00A024541EE3}``]
"Compatibility Flags"=dword:00000400
Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this and other ActiveX vulnerabilities. Instructions for disabling ActiveX in the Internet Zone can be found in the "Securing Your Web Browser" document.

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Vendor Information

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Updated: January 04, 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

Citrix has provided updated versions of the affected software to address this issue. Please see the corresponding Citrix Security Bulletin for more information.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23210969 Feedback>).

CVSS Metrics

Group	Score	Vector
Base
Temporal
Environmental

References

• <http://www.fortconsult.net/images/pdf/citrix_advisory_dec2006.pdf&gt;
• <http://www.tippingpoint.com/security/advisories/TSRT-06-15.html&gt;
• <http://support.citrix.com/article/CTX111827&gt;

Acknowledgements

Thanks to Andrew Christensen of the FortConsult security research team for reporting this vulnerability. This issue was also independently reported by Aaron Portnoy of the TippingPoint Security Research Team.

This document was written by Chad R Dougherty.

Other Information

CVE IDs:	CVE-2006-6334
Date Public:	2006-11-29 Date First Published: