-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, This is Cisco PSIRT response to the statements made by Thomas Liam Romanis of Fujitsu Services Limited in their posting to BugTraq on the 15th June 2006, regarding Cisco Secure ACS LoginProxy.CGI Cross-Site Scripting Vulnerability, located at http://www.securityfocus.com/bid/18449/info. An official response is location at: http://www.cisco.com/warp/public/707/cisco-sr-20060615-acs.shtml This vulnerability is addressed by Cisco Bug ID: * CSCsd50560 -- ACS LogonProxy.cgi vulnerable to Cross Site Scripting attacks. We would like to thank Thomas Liam Romanis and Fujitsu Services Limited for reporting this vulnerability to us. We greatly appreciate the opportunity to work with researchers on security vulnerabilities, and welcome the opportunity to review and assist in product reports. Additional Information ====================== Cisco Secure Access Control Server (ACS) is a centralized user access control framework. Cisco Secure ACS offers centralized command and control for all user authentication, authorization, and accounting (AAA pronounced "triple A") services to network devices that function as AAA clients. Cisco Secure ACS for UNIX LogonProxy.cgi is vulnerable to Cross Site Scripting (XSS) attacks via both HTML GET and POST requests. This vulnerability affects only Cisco Secure ACS for Unix. Cisco Secure ACS for Windows and Cisco Secure ACS Solution Engine are not affected. This vulnerability could be used to redirect the ACS administrative users to another host which could be used to proxy logon requests back to the bona fide ACS server while harvesting administrative user credentials. Solution ======== Download and apply patch for CSCsd50560, which is located on Cisco.com at: http://www.cisco.com/cgi-bin/tablebuild.pl/cspatchunix-3des Instructions for applying the patch are found at the same location. The following best practices will help mitigate the risks of this vulnerability: * Ensure that only IP addresses of trusted administrator hosts can access the Cisco Secure ACS server. * Prevent access to the web component of the ACS server over the Internet. Regards Paul Oxman Cisco Systems PSIRT - -----Original Message----- From: liam.romanis (at) uk.fujitsu (dot) com [email concealed] [mailto:liam.romanis (at) uk.fujitsu (dot) com [email concealed]] Sent: Friday, 16 June 2006 1:03 AM To: bugtraq (at) securityfocus (dot) com [email concealed] Subject: Cisco Secure ACS Cross Site Scripting Vulnerability. FUJITSU SERVICES SECURITY ADVISORY DATE: 27-01-2006 AUTHOR: THOMAS LIAM ROMANIS VENDOR: Cisco PRODUCT: Cisco Secure ACS VERSION(S) TESTED: Cisco Secure ACS version 2.3 UNIX hosted on Netscape FastTrack Server version 2.01c on Sun Solaris 8.0 TITLE: Cisco Secure ACS LogonProxy.cgi Cross Site Scripting vulnerability. Summary: Cisco Secure ACS LoginProxy.cgi has been found to be vulnerable to Cross Site Scripting attacks via both GET and POST requests due to a failure to properly filter undesirable user input. Successful exploitation could result in a loss of privacy of sensitive data, such as usernames and passwords. Detail: Exploitation of this type of attack relies on the attacker's ability to inject code (in this case java script) into the HTML that is delivered to the user's Internet Browser. In this case it is possible to craft POST and GET requests to LogonProxy.CGI that result in detailed errors being presented in which the requested URL (or Query) is displayed. Thus, it is possible to inject java script into the error message which could be utilised to execute a Cross Site Scripting attack. In this case the attack could not be used to steal session information (as it is commonly used) but it could be used to redirect the user to another host. A possible scenario would be that the user is redirected to a host owned by the attacker which hosts a copy of the Cisco Secure ACS front end. This would then be used to proxy logon requests back to the bone fide server whilst harvesting administrative user credentials. Exploitation: The following test scripts could be used to ascertain whether the system under test is vulnerable: 1. POST Request. POST http://10.17.12.184:80/CScgi/LogonProxy.cgi HTTP/1.0 Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, */* Referer: http://10.17.12.184/cs/index.html Accept-Language: en-gb Content-Type: application/x-www-form-urlencoded Proxy-Connection: Keep-Alive User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.0.3705; .NET CLR 1.1.4322) Host: 10.17.12.184 Content-Length: 33 Pragma: no-cache Server=0.0.0.0&error=<script>alert("help")</script> 2. GET Requests. http://10.17.12.184/CScgi/LogonProxy.cgi?Server=0.0.0.0&error=<script>al ert("help")</script> http://10.17.12.184/CScgi/LogonProxy.cgi?Server=10.17.12.184/Logon?null& SSL=<script>alert('help')</script> http://10.17.12.184/CScgi/LogonProxy.cgi?Ok=<script>alert('help')</scrip t> Recommendations: (Until patch information is available). These recommendations are based on Cisco Secure ACS being used on an internal network rather than an internet facing system. * If possible reconfigure the system so that detailed error messages are not displayed in the user's internet browser. * Network Architecture Design should ensure that only the IP addresses of hosts used by bone fide Cisco Secure ACS users/Administrators can connect to these services. * Consider dissemination of the attack string along side of controls in place on systems such as e-mail (spoofing and HTML e-mail), Vulnerable web services (publication/uploading of malicious code), exploitable applications (eg: guestbooks) and code published in MS Office document types. * Consider whether current controls on desktops and servers are adequate to prevent users from installing and controlling their own network services. Recommendations supplied to the Vendor: Logonproxy.cgi needs to have addition code added to filter out undesirable requests. The characters which should be filtered in all forms (i.e. ASCII and UNICODE etc) to avoid Cross Site Scripting attacks are: <,>,>,<,(,),",/,=,:,;, Vendor Recommendations: A new version of fastadmin.zip will be made available by Cisco at the following location: http://www.cisco.com/warp/public/707/cisco-sr-20060615-acs.shtml Once you have downloaded this follow these instructions: Steps to install the patch: =========================== 1) Stop the Ciscosecure process using $BASEDIR/utils/kcs 2) Create a backup of the existing file $BASEDIR/FastAdmin/fastadmin.zip 3) Copy the patch(fastadmin.zip) to the location $BASEDIR/FastAdmin 4) Start the CiscoSecure process using $BASEDIR/utils/scs Final Comments: Fujitsu Services would like to thank Paul Oxman and Cisco for their cooperation and professionalism. -----BEGIN PGP SIGNATURE----- Version: PGP 8.1 iQA/AwUBRJPeslNe5xf4YEH7EQKwTQCdFz964bRw3kNCcVXmmW1w067tTRYAnjQI jjvLrnv49chyepdTUaVqgJlV =S3dw -----END PGP SIGNATURE-----