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In their advisory below, Marc and Stefan illustrate how to bypass the
application firewall used in Cisco CallManager. This means of bypass can be
used to display graphics, scripts, or other information downloaded from an
external web site. This technique may also be used to conduct cross-site scripting attacks. Cisco confirms that the example the authors provided bypasses the web application firewall and that there may be other methods
for bypassing the web application firewall.
Cisco has made improvements to the input validation mechanisms in
CallManager that may mitigate the risks associated with this security
vulnerability. These improvements have been incorporated into 4.2(3)sr2.
Future releases, 3.3(5)sr3, 4.1(3)sr5 and 4.3(1)sr1, will also include
improvements made to address this bug. This issue is being tracked by the
following Cisco Bug ID:
Service releases of CallManager software are available at the following link:
Cisco CallManager is the software-based call-processing component of the
Cisco IP telephony solution that extends enterprise telephony features
functions to packet telephony network devices, such as IP phones, media processing devices, voice-over-IP (VoIP) gateways, and multimedia applications. The vulnerability described in this response exists in the web application firewall used in CallManager. This feature is designed to
prevent users from entering malicious code into the input fields used in CallManager forms. The vulnerability exists because the web application firewall fails to properly sanitize some potentially malicious tags.
To exploit these issues an attacker must convince an authenticated user
follow a specially crafted, malicious URL. A successful attack may result
in the execution of arbitrary script code in the user's web browser.
For additional information on cross-site scripting (XSS) attacks and the methods used to exploit such vulnerabilities, please refer to the Cisco Applied Intelligence Response "Understanding Cross-Site Scripting (XSS) Threat Vectors," which is available at the following link:
The Cisco PSIRT is not aware of any malicious use of the vulnerability described in this document.
We would like to thank Marc Ruef and Stefan Friedi for bringing this
to our attention and for working with us toward coordinated disclosure of
the issue. We greatly appreciate the opportunity to work with researchers
on security vulnerabilities, and welcome the opportunity to review and assist in product reports.
Product Security Incident Response Team (PSIRT) Cisco Systems, Inc.
Cisco CallManager 4.1 Input Validation Vulnerability
scip AG Vulnerability ID 2977 (03/13/2007) http://www.scip.ch/cgi-bin/smss/showadvf.pl?id=2977
I. INTRODUCTION Cisco CallManager, short CCM, is a professional voice-over-IP solution that tracks active components, including among others phones, gateways, conference bridges, transcoding resources and voicemail boxes.
II. DESCRIPTION Marc Ruef and Stefan Friedli found a web-based vulnerability that was identified in Cisco CallManager 4.1 and may affect earlier versions as well.
The web interface of the application fails to properly santisize data supplied by the search-form before displaying it back to the user. Though several filters are in place to prevent the injection of <script> Tags or action handlers such as "onclick" or "onmouseover", it is possible to inject html-code including common attributes. This allows the embedding of external references, e.g. images or flash resources. The vulnerability also allows an attacker to use the "style"-attribute on any tag to conduct arbitrary web-based attacks.
IV. IMPACT This vulnerability may be exploited by tricking authenticated users into clicking a crafted link in order to conduct arbitrary web-based attacks.
V. DETECTION Detection of web based attacks requires a specialized web proxy and/or intrusion detection system. Patterns for detection of basic attacks are available and easy to implement, though they may possibly fail on more sophisticated attacks.
VI. SOLUTION Server-side input validation should be improved to prevent the injection of unauthorized code. Cisco has taken appropriate steps regarding this issue, see vendor response (VII) for details.
VII. VENDOR RESPONSE A representative of the Cisco Product Security Incident Response Team (PSIRT) stated, that this kind of exploitation is blocked by improvements to the web application firewall used in CallManager. The Cisco PSIRT team has issued a formal security response available at: http://www.cisco.com/warp/public/707/cisco-sr-20070523-ccm.shtml.
VIII. SOURCES scip AG - Security Consulting Information Process (german) http://www.scip.ch
scip AG Vulnerability Database (german)
IX. DISCLOSURE TIMELINE 03/13/07 Identification of the vulnerabilities 03/13/07 Notification of the vendor 03/14/07 Response from Mark-David McLaughlin [firstname.lastname@example.org] of the PSIRT 03/19/07 Status Notification by PSIRT 03/28/07 Status Notification by PSIRT 04/18/07 Status Notification by PSIRT 04/20/07 Status Notification by PSIRT 05/02/07 Status Notification by PSIRT 05/05/07 Coordination of public release 05/16/07 Final Vendor Response received 05/23/07 Public Release
IX. CREDITS The vulnerabilities were discovered by Marc Ruef and Stefan Friedli. Marc Ruef, scip AG, Zuerich, Switzerland maru-at-scip.ch http://www.scip.ch Stefan Friedli, scip AG, Zuerich, Switzerland stfr-at-scip.ch http://www.scip.ch Thanks to Mark-David McLaughlin (PSIRT) for cooperating.
A2. LEGAL NOTICES Copyright (c) 2007 scip AG, Switzerland.
Permission is granted for the re-distribution of this alert. It may not be edited in any way without permission of scip AG.
The information in the advisory is believed to be accurate at the time of publishing based on currently available information. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect or consequential loss or damage from use of or reliance on this advisory.
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