Input Validation/Output Encoding Vulnerabilities in Cisco CallManager Allow Script Injection Attacks

2006-06-22 / 2006-06-23
Risk: High
Local: No
Remote: Yes
CWE: CWE-Other

CVSS Base Score: 4.3/10
Impact Subscore: 2.9/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: None
Integrity impact: Partial
Availability impact: None

I. SYNOPSIS Release Date: 07/19/2006 Affected Application: Cisco CallManager 3.1 and up (versions prior to 3.1 were not tested but may still be vulnerable) Severity If Exploited: High Impact: Arbitrary configuration of phone system/Theft of individual phone users' credentials Mitigating Factors: Requires user action (following a link, visiting a resource with an embedded redirect) Initial Notification of Vendor: 10/24/2005 Discovery: Jake Reynolds, Senior Security Engineer -- FishNet Security Contributions: Arian Evans, Senior Security Engineer - FishNet Security Permanent Advisory Location: XSS+Advisory.htm II. EXECUTIVE SUMMARY Vulnerability Overview: The web interface used to administer Cisco CallManager software suffers from a lack of input validation and output encoding. As a result, an attacker could craft a request that causes the CallManager web interface to include malicious JavaScript in its response. If a victim can be made to submit this specially crafted request, the response will be processed, and the malicious JavaScript payload executed in the browser of the victim. Attack Overview: If such a request is provided to CallManager administrators (either in an email or embedded in an html resource using something like an automatic redirect) an attacker can perform a variety of nefarious actions. Depending on the scripted payload, these attacks are commonly referred to as cross-site scripting (XSS), session riding, and cross-site request forgery (CSRF). Potential threats that can be realized through these vulnerabilities could include but are not limited to: * Deletion of phone system components such as devices, partitions, calling search spaces, etc * Reconfiguration of phone system components such as route plans, global directory, services, etc * Theft of global directory user credentials * Theft of "Cisco CallManager User Options" credentials or session token leading to user identity spoofing within that specific interface of CallManager (Utilization of the stolen credentials or session tokens would require direct connectivity to CallManager.) III. TECHNICAL DETAIL Vulnerability Details: The web interfaces used to administer Cisco CallManager exhibit input validation/output encoding vulnerabilities throughout the applications. Specifically, the "Cisco CallManager Administration" and "Cisco CallManager User Options" interfaces contain multiple instances of these vulnerabilities. This advisory will focus on a subset of those vulnerabilities that allow attack execution from an unauthenticated perspective. Not all vulnerability instances will be included. The "Cisco CallManager Administration" (http://CallManagerAddress/ccmadmin/) web interface contains parameters that have their user-supplied input returned in subsequent responses without being properly encoded. Although this interface requires basic authentication before access to the vulnerable parameters is granted, the original request will be sent to the server after successful authentication. Thus, reflected script injection is possible if the attacker can lure a CallManager administrator into entering their credentials upon being presented with the basic authentication box. The URL below takes advantage of the vulnerable "pattern" parameter that returns user-supplied input at several points within the subsequent responses. http://CallManagerAddress/ccmadmin/phonelist.asp?findBy=description&matc h=begins&pattern=<script>alert (document.cookie)</script>&submit1=Find&rows=20&wildcards=on&utilityList = A simple proof of concept script has been written that utilizes XMLHTTP to search for devices and delete them from the CallManager configuration. Prior knowledge of the CallManager configuration would allow for more savvy attacks that could intelligently reconfigure the phone system. The "Cisco CallManager User Options" (http://CallManagerAddress/ccmuser/) web interface also contains vulnerable parameters. Most notably, arbitrary parameters included in requests to /ccmuser/logon.asp are returned by the application without proper input validation or output encoding. The URL below takes advantage of this behavior by appending the parameter "MadeUpParameter", escaping the form included in the response, and rewriting all form actions to point to an attacker site that collects all input. The application seems to remove the '+' character used to post-increment the loop counter so URL hex encoding (%2B) was used to obfuscate it. http://CallManagerAddress/ccmuser/logon.asp?userID=&password=&MadeUpPara meter="><script>for (i=0; i<document.forms.length; i%2B%2B) document.forms[i].action="";</ script><!-- By luring phone system users into making the above request and logging in, an attacker can steal their credentials. IV. MITIGATING FACTORS Prerequisites: In all cases, there is some prerequisite information that an attacker must have. The address of the CallManager is obviously a necessity in order to correctly craft malicious requests. This could be easily gained internally by viewing the network configuration on the IP phones that register with the targeted CallManager unless the display of this information has been disabled. Social engineering could allow an attacker to gain this information from inside or outside of the organization. It is important to note that while the address of the target CallManager is required, the attacker does not require connectivity. Reflected script injection attacks only require that the victim has connectivity to the vulnerable application, since the victim is the entity that makes the malicious request, causing unwanted execution of the script included in the vulnerable server's response. Any intelligent reconfiguration of Cisco CallManager using CSRF attacks as mentioned above would require knowledge of the current CallManager configuration. However, a significant amount of damage could be inflicted by an XMLHTTP-based script that searches for and deletes all devices without prior knowledge of the current CallManager configuration. Exploitation of the "Call Manager User Options" logon page does not require connectivity to the target CallManager. However, the use of stolen credentials gained through such an attack would require connectivity to a system that utilizes them. This system, in many cases might only be the CallManager itself. However, in the case of CallManager integration with another directory such as iPlanet or Active directory, credential theft could lead to an attacker gaining access to many other services. V. RECOMMENDED ACTIONS Technical Workarounds: * Upgrade Software When Fixes Become Available - Cisco has stated that future releases of all trains of Cisco CallManager will contain fixes for these vulnerabilities. * Restrict Network Connectivity to CallManager Interfaces - During discovery, it was noted that several organizations had their CallManager administration interfaces exposed to the Internet. Simple Google queries are all an attacker needs in this case to obtain the target CallManager address. There are few compelling reasons one could present that would justify public access to CallManager web interfaces. * Treat Sensitive/Critical Interfaces as Sensitive & Critical - Information about the specifics of the CallManager configuration should be kept confidential. Access to the various CallManager interfaces should be as restrictive as possible. Although these attacks do not require an attacker to have connectivity to the vulnerable application, restriction of this access still serves to limit attack vectors by limiting the amount of potential victims. Nontechnical Workarounds: * Education & Awareness of User Luring Attack Vector - Educate all users about the risks of social engineering attacks. Users should be aware of the triviality of spoofing emails, caller ID, and other types of information. VI. CONTACT You can reach the author of this advisory by emailing jake[dot]reynolds[at]

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