Cisco Security Advisory: IOS HTTP Server Command Injection Vulnerability

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Cisco Security Advisory: IOS HTTP Server Command Injection Vulnerability ======================================================================== Document ID: 68322 Advisory ID: cisco-sa-20051201-http http://www.cisco.com/warp/public/707/cisco-sa-20051201-http.shtml Revision 1.0 For Public Release 2005 December 01 2100 UTC (GMT) - ----------------------------------------------------------------------- Contents ======== Summary Affected Products Details Impact Software Versions and Fixes Workarounds Obtaining Fixed Software Exploitation and Public Announcements Status of This Notice: INTERIM Distribution Revision History Cisco Security Procedures - ----------------------------------------------------------------------- Summary ======= A vulnerability exists in the IOS HTTP server in which HTML code inserted into dynamically generated output, such as the output from a "show buffers" command, will be passed to the browser requesting the page. This HTML code could be interpreted by the client browser and potentially execute malicious commands against the device or other possible cross-site scripting attacks. Successful exploitation of this vulnerability requires that a user browse a page containing dynamic content in which HTML commands have been injected. Cisco will be making free software available to address this vulnerability for affected customers. There are workarounds available to mitigate the effects of the vulnerability. This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20051201-http.shtml. Affected Products ================= This security advisory applies to all Cisco products that run Cisco IOS Software versions 11.0 through 12.4 with the HTTP server enabled. A system which contains the IOS HTTP server or HTTP secure server, but does not have it enabled, is not affected. To determine if the HTTP server is running on your device, issue the "show ip http server status" and "show ip http server secure status" commands at the prompt and look for output similar to: Router>show ip http server status HTTP server status: Enabled If the device is not running the HTTP server, you should see output similar to: Router>show ip http server status HTTP server status: Disabled Any version of Cisco IOS prior to the versions which will be listed in the Fixed Software section below may be vulnerable. Cisco IOS XR is not affected. To determine the software running on a Cisco product, log in to the device and issue the "show version" command to display the system banner. Cisco IOS Software will identify itself as "Internetwork Operating System Software" or simply "IOS". On the next line of output, the image name will be displayed between parentheses, followed by "Version" and the IOS release name. Other Cisco devices will not have the "show version" command or will give different output. The following example identifies a Cisco product running IOS release 12.3(6) with an installed image name of C3640-I-M: Cisco Internetwork Operating System Software IOS (tm) 3600 Software (C3640-I-M), Version 12.3(6), RELEASE SOFTWARE (fc3) The next example shows a product running IOS release 12.3(11)T3 with an image name of C3845-ADVIPSERVICESK9-M: Cisco IOS Software, 3800 Software (C3845-ADVIPSERVICESK9-M), Version 12.3(11)T3, RELEASE SOFTWARE (fc4) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2005 by Cisco Systems, Inc. Additional information about Cisco IOS release naming can be found at http://www.cisco.com/warp/public/620/1.html. No other Cisco products are currently known to be affected by the vulnerability addressed in this advisory. Details ======= The Cisco IOS Web browser interface (which enables the device to perform as an HTTP server) allows configuration and monitoring of a router or access server using any web browser. This feature was introduced in IOS 11.0. A vulnerability exists in the IOS HTTP server in which HTML code inserted into dynamically generated output, such as the output from a "show buffers" command, will be passed to the browser requesting the page. This HTML code could be interpreted by the browser and potentially execute malicious commands against the device or other possible cross-site scripting attacks. In order to be vulnerable to the cross-site scripting attack, a user must browse and view the content during the same period of time the injected code exists in memory. On the other hand, if a user does not browse contaminated dynamic content on the device, then exploitation is not possible. A proof of concept exploit exists for this vulnerability, in which the exploit attempts to reset the enable password on the device. For the attack to work against the device itself, the user browsing tainted dynamic content on the router will only be able to execute commands at or below the privilege level for which they are authenticated and authorized for on the device. This vulnerability is documented in Cisco Bug ID CSCsc64976. Impact ====== Successful exploitation of the vulnerability may result in an attacker executing commands on the device, including the possibility of gaining full administrative privileges on the device which is dependent on the privilege level of the authenticated user. Software Versions and Fixes =========================== No software fixes are currently available. This section will be updated regularly as soon as software fixes are available. Workarounds =========== Disable the HTTP server +---------------------- If the HTTP server is not used for any legitimate purposes on the device, it is a best practice to disable it by issuing the following commands in configure mode: no ip http server no ip http secure-server Disable the HTTP WEB_EXEC service +-------------------------------- A feature was introduced in 12.3(14)T and later in which selective HTTP and HTTPS services could be enabled or disabled. Two typical services are WEB_EXEC and the IOS Certificate Server (SCEP). The WEB_EXEC service provides a facility to configure the box and retrieve current state of the box from remote clients. The IOS Certificate Server service provides a facility wherein remote clients can enroll and obtain Crypto Certificates. It is possible to disable the WEB_EXEC service while still leaving SCEP running to serve Certificates. If an installation requires the use of the SCEP service, the WEB_EXEC service may be disabled via the commands in configure mode: no ip http active-session-modules WEB_EXEC no ip http secure-active-session-modules WEB_EXEC Avoid the use of Web-based SHOW commands +--------------------------------------- Successful exploitation of this vulnerability requires an unsuspecting user to request dynamic content from the device via the "show" commands which are available. Avoiding the use of those commands via the web interface until an upgrade to fixed software is possible may be perfectly legitimate for some installations. Obtaining Fixed Software ======================== Cisco will make free software available to address this vulnerability for affected customers. This advisory will be updated as fixed software becomes available. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment. Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/public/sw-license-agreement.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml. Do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. Customers with Service Contracts +------------------------------- Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com. Customers using Third-party Support Organizations +------------------------------------------------ Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory. The effectiveness of any workaround or fix is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed. Customers without Service Contracts +---------------------------------- Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third-party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows. * +1 800 553 2447 (toll free from within North America) * +1 408 526 7209 (toll call from anywhere in the world) * e-mail: tac@cisco.com Have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC. Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages. Exploitation and Public Announcements ===================================== This vulnerability was disclosed in a public posting to the Bugtraq mailing list, and at the following URL: http://www.infohacking.com/INFOHACKING_RESEARCH/Our_Advisories/cisco/index.h.... The Cisco PSIRT is not aware of any malicious use of the vulnerability described in this advisory. Status of This Notice: INTERIM ============================== THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME. CISCO EXPECTS TO UPDATE THIS DOCUMENT WITHIN FROM THE ORIGINAL DATE OF THIS NOTICE. A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors. Distribution ============ This advisory is posted on Cisco's worldwide website at http://www.cisco.com/warp/public/707/cisco-sa-20051201-http.shtml. In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients. * cust-security-announce@cisco.com * first-teams@first.org * bugtraq@securityfocus.com * vulnwatch@vulnwatch.org * cisco@spot.colorado.edu * cisco-nsp@puck.nether.net * full-disclosure@lists.grok.org.uk * comp.dcom.sys.cisco@newsgate.cisco.com Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates. Revision History ================ +----------------------------------------+ | Revision | 1-December-2005. | Initial | | 1.0 | | draft. | +----------------------------------------+ Cisco Security Procedures Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.h.... This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt/. - ----------------------------------------------------------------------- All contents are Copyright 1992-2005 Cisco Systems, Inc. All rights reserved. - ----------------------------------------------------------------------- Updated: Dec 01, 2005 Document ID: 68322 - ----------------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) iD8DBQFDj3udezGozzK2tZARAmkwAJ4xrlLCF75ryXyuX2/62peJ1YAUegCfYdUS jfZM0o9w1mRIAVF4C3uunRs= =A852 -----END PGP SIGNATURE-----