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TUCoPS :: Cisco :: ciacl012.htm

Cisco IOS HTTP Server Query Vulnerability



Cisco IOS HTTP Server Query Vulnerability Privacy and Legal Notice

CIAC INFORMATION BULLETIN

L-012: Cisco IOS HTTP Server Query Vulnerability

October 26, 2000 22:00 GMT
PROBLEM:       Cisco had identified a defect in multiple releases of Cisco IOS
               software.
PLATFORM:      All mainstream Cisco routers and switches running Cisco IOS
               software releases 12.0 through 12.1, inclusive.
DAMAGE:        If the enable password is known or not set, the defect could be
               exploited to produce a denial of service (DoS) attack.
SOLUTION:      Until software patches become available, implement appropriate
               workaround as indicated by Cisco below.

VULNERABILITY The risk is MEDIUM. This vulnerability may only be exploited if ASSESSMENT: the enable password is not set, it is well known, or it can be guessed. The vulnerability is publicly known.
[****** Start of Cisco Bulletin ******] Cisco IOS HTTP Server Query Vulnerability Revision 1.0 For public release 2000 October 25 at 08:00 US/Pacific (UTC+0700) _________________________________________________________________ Summary A defect in multiple releases of Cisco IOS software will cause a Cisco router or switch to halt and reload if the IOS HTTP service is enabled, browsing to "http://router-ip/anytext?/" is attempted, and the enable password is supplied when requested. This defect can be exploited to produce a denial of service (DoS) attack. The vulnerability, identified as Cisco bug ID CSCdr91706, affects virtually all mainstream Cisco routers and switches running Cisco IOS software releases 12.0 through 12.1, inclusive. This is not the same defect as CSCdr36952. The vulnerability has been corrected and Cisco is making fixed releases available for free to replace all affected IOS releases. Customers are urged to upgrade to releases that are not vulnerable to this defect as shown in detail below. This vulnerability can only be exploited if the enable password is known or not set. The complete advisory is available at http://www.cisco.com/warp/public/707/ioshttpserverquery-pub.shtml . Affected Products The following products are affected if they run a Cisco IOS software release that has the defect. To determine if a Cisco product is running an affected IOS, log in to the device and issue the command show version. Cisco IOS software will identify itself as "Internetwork Operating System Software" or "IOS (tm)" software and will display a version number. Other Cisco devices either will not have the command show version, or will give different output. Compare the version number obtained from the router with the versions presented in the Software Versions and Fixes section below. Cisco devices that may be running with affected IOS software releases include: * Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 800, ubr900, 1000, 1400, 1500, 1600, 1700, 2500, 2600, 3000, 3600, 3800, 4000, 4500, 4700, AS5200, AS5300, AS5800, 6400, 7000, 7200, ubr7200, 7500, and 12000 series. * Most recent versions of the LS1010 ATM switch. * The Catalyst 6000 if it is running IOS. * The Catalyst 2900XL LAN switch only if it is running IOS. * The Cisco DistributedDirector. For some products, the affected software releases are relatively new and may not be available on every device listed above. If you are not running Cisco IOS software, you are not affected by this vulnerability. Cisco products that do not run Cisco IOS software and are not affected by this defect include, but are not limited to: * 700 series dialup routers (750, 760, and 770 series) are not affected. * Catalyst 1900, 2800, 2900, 3000, and 5000 series LAN switches are not affected, except for some versions of the Catalyst 2900XL. However, optional router modules running Cisco IOS software in switch backplanes, such as the RSM module for the Catalyst 5000 and 5500, are affected (see the Affected Products section above). * The Catalyst 6000 is not affected if it is not running IOS. * WAN switching products in the IGX and BPX lines are not affected. * The MGX (formerly known as the AXIS shelf) is not affected. * No host-based software is affected. * The Cisco PIX Firewall is not affected. * The Cisco LocalDirector is not affected. * The Cisco Cache Engine is not affected. Details The HTTP server was introduced in IOS release 11.0 to extend router management to the worldwide Web. The "?" (question mark) character is defined in the HTML specifications as a delimiter for CGI arguments. It is also interpreted by the IOS command-line interface as a request for help. As of Cisco IOS Software Release 12.0T, the meaning of a question mark when it appears adjacent to a "/" (slash) character cannot be determined properly by the URI parser in affected versions of Cisco IOS software. When a URI containing "?/" is presented to the HTTP service on the router and a valid enable password is supplied, the router enters an infinite loop. A watchdog timer expires two minutes later and forces the router to crash and reload. The router continues to be vulnerable to this defect as long as it is running an affected IOS software release and the enable password is known. This vulnerability may only be exploited if the enable password is not set, it is well known, or it can be guessed. In rare cases, an affected device fails to reload, which means an administrator must physically cycle the power to resume operation. The HTTP server is not enabled by default except on unconfigured Cisco model 1003, 1004, and 1005 routers. Once initial access is granted to configure the router, the customer may set an enable password, and disable or limit access to the HTTP server by changing the configuration. Once the new configuration has been saved, the HTTP server will not be enabled when the router restarts. Impact An affected Cisco IOS device that is operating with the HTTP service enabled and is not protected by having the enable password configured can be forced to halt for up to two minutes and then reload. The vulnerability can be exercised repeatedly, possibly creating a denial of service (DOS) attack, unless the service is disabled, the enable password is set, or the router is upgraded to a fixed release. In instances in which a router at a remote location fails to reload, an administrator must visit the site to enable the device to recover from the defect. Software Versions and Fixes The following table summarizes the Cisco IOS software releases affected by the defect described in this notice and scheduled dates on which the earliest corresponding fixed releases will be available. Dates are tentative and subject to change. Each table row shows the earliest release that contains the fix in the "Rebuild", "Interim", or "Maintenance" columns, presented in release number order. A Maintenance Release is the most heavily tested and highly recommended release. A Rebuild Release is constructed from a previous maintenance or mainline release and contains a code fix for a specific defect. Although it receives less testing than a maintenance release, it is built from a previous maintenance release and includes minimum changes to address a specific defect. An Interim Release has much less testing than a maintenance release and should be selected only if no other suitable release fixes the defect. In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. +==========+=================+==============================================+ | Major | Description or | | | Release | Platform | Availability of Repaired Releases* | +==========+=================+===============+==============+===============+ |Unaffected Earlier Releases | Rebuild | Interim** | Maintenance | +==========+=================+===============+==============+===============+ |11.0 & | | | | | |earlier, | | |Not | | |all |Numerous |Not vulnerable |vulnerable |Not vulnerable | |variants | | | | | +----------+-----------------+---------------+--------------+---------------+ | |11.1 AA, 11.1 | | | | |11.1 |CA, 11.1 CC, |Not vulnerable |Not |Not vulnerable | | |11.1 CT, 11.1 IA | |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ | |11.2 SA, 11.2 | | | | |11.2 |BC, 11.2 P, 11.2 |Not vulnerable |Not |Not vulnerable | | |F, 11.2 GS, 11.2 | |vulnerable | | | |WA3, 11.2 XA | | | | +----------+-----------------+---------------+--------------+---------------+ | |11.3 NA, 11.3 | | | | | |AA, 11.3 DA, | | | | |11.3 |11.3 XA, 11.3 |Not vulnerable |Not |Not vulnerable | | |HA, 11.3 WA, | |vulnerable | | | |11.3 MA, 11.3 DB | | | | +==========+=================+===============+==============+===============+ | 12.0-based Releases | Rebuild | Interim** | Maintenance | +==========+=================+===============+==============+===============+ | |General | | | | |12.0 |Deployment (GD): |Not vulnerable |Not |Not vulnerable | | |all platforms | |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ |12.0DA |xDSL support: |Not vulnerable | Not | Not vulnerable| | |6100, 6200 | |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ | |Core/ISP | | | | |12.0S |support: gsr, |Not vulnerable |Not |Not vulnerable | | |rsp, c7200 | |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ |12.0SC |Cable/broadband | Not |Not |Not vulnerable | | |ISP: ubr7200 |vulnerable |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ |12.0SL |10000 ESR: c10k |Not vulnerable |Not |Not vulnerable | | | | |vulnerable | | +----------+-----------------+---------------+--------------+---------------+ | |Early | | | | | |Deployment(ED): | | | | |12.0T |VPN, Distributed | | | | | |director, | | | | | |various | | |Unknown | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |cat8510c, | | | | | |cat8540c, c6msm | | | | | | | | |12.0(13)W5(19) | | |ls1010, | | | | | |cat8510m, | | | | | |cat8540m | | +---------------+ | |c5atm, c5atm, | | | | |12.0W5 |c3620, c3640, | | | | | |c4500, c5rsfc, | | |2000-NOV-13 | | |c5rsm, c7200, | | | | | |rsp | | | | +----------+-----------------+---------------+--------------+---------------+ | |cat2948g, | | |12.0(10)W5(18e)| | |cat4232 | | +---------------+ | | | | |2000-NOV-14 | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.0XA |(ED): limited | | |12.1(5) | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment |12.1(3a)E4 | | | |12.0XE |(ED): limited +---------------+ | | | |platforms |2000-OCT-24 | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment |12.0(4)XH4 | | | |12.0XH |(ED): limited +---------------+ | | | |platforms |Unknown | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment |12.0(5)XJ6 | | | |12.0XJ |(ED): limited +---------------+ | | | |platforms |Unknown | | | +==========+=================+===============+==============+===============+ | 12.1-based Releases | Rebuild | Interim** | Maintenance | +==========+=================+===============+==============+===============+ | |General | | |12.1(05) | |12.1 |Deployment (GD) | | | | | |candidate: all | | +---------------+ | |platforms | | |2000-OCT-30 | +----------+-----------------+---------------+--------------+---------------+ | |Access & Dial |12.1(4)AA1 | | | | |Early Deployment | | | | |12.1AA |(ED): c5200, +---------------+ | | | |c5300, c5800, |Unknown | | | | |dsc-c5800 | | | | +----------+-----------------+---------------+--------------+---------------+ | | | | |12.01(04)DA | |12.1DA |xDSL support: | | | | | |6160, 6260 | | +---------------+ | | | | |2000-OCT-30 | +----------+-----------------+---------------+--------------+---------------+ | | | | |12.01(4)DB | |12.1DB |xDSL support: | | | | | |c6400 | | +---------------+ | | | | |2000-NOV-13 | +----------+-----------------+---------------+--------------+---------------+ | | | | |12.01(4)DC | |12.1DC |xDSL NRP | | | | | |support: c6400r | | +---------------+ | | | | |2000-NOV-13 | +----------+-----------------+---------------+--------------+---------------+ | |ELB Early |12.1(3a)E4 | | | | |Deployment (ED): | | | | |12.1E |cat6k, 8500, +---------------+ | | | |ls1010, 7500, |2000-OCT-24 | | | | |7200, 7100 | | | | +----------+-----------------+---------------+--------------+---------------+ | |Cable/broadband | 12.01(03a)EC1 | | | |12.1EC |Early Deployment +---------------+ | | | |(ED): ubr7200 | Unknown | | | +----------+-----------------+---------------+--------------+---------------+ | |New technology | | 12.1(5.0.x)T | 12.1(5)T | |12.1T |Early Deployment | | | | | |(ED): all | +--------------+---------------+ | |platforms | | Unknown | Unknown | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XA |(ED): limited | Not scheduled | | 12.1(5)T | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XB |(ED): limited | Not scheduled | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | | Early | | | | | 12.XC |Deployment (ED): |Not scheduled | | 12.1(5)T | | |limited | | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XD |(ED): limited |Not scheduled | | 12.1(5)T | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XE |(ED): limited |Not scheduled | | 12.1(5)T | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XF |(ED): limited |Not scheduled | | 12.1(5)T | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XG |(ED): limited |Not scheduled | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XH |(ED): limited |Not scheduled | | 12.1(5)T | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XI |(ED): limited |Not scheduled | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XJ |(ED): limited |Not scheduled | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XL |(ED): limited |Not scheduled | | | | |platforms | | | | +----------+-----------------+---------------+--------------+---------------+ | |Early Deployment | | | | |12.1XP |(ED): limited |Not scheduled | | 12.1(5)T | | |platforms | | | | +==========+=================+===============+==============+===============+ | Notes | +===========================================================================+ |* All dates are estimated and subject to change. | +---------------------------------------------------------------------------+ |** Interim releases are subjected to less rigorous testing than regular | |maintenance releases, and may have serious bugs. | +===========================================================================+ Obtaining Fixed Software Cisco offers free software upgrades to affected customers to remedy this vulnerability. Customers with service contracts may upgrade to any software release. Customers without contracts may upgrade only within a single row of the table above, except that any available fixed software release will be provided to any customer who can use it and for whom the standard fixed software release is not yet available. Customers may install only the feature sets they have purchased. Not all fixed software may be available as of the release date of this notice. Customers with contracts should obtain upgraded software through regular update channels. Most customers can obtain upgrades via the Software Center on Cisco's Worldwide Web site at http://www.cisco.com/. Customers without contracts should obtain their upgrades by contacting the Cisco Technical Assistance Center (TAC) as follows: * +1 800 553 2447 (toll-free call within North America) * +1 408 526 7209 (toll call from elsewhere in the world) * E-mail: tac@cisco.com Additional contact information for the TAC is on-line at http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml, including instructions and e-mail addresses for use by non-English speakers. Give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for noncontract customers must be requested through the TAC. Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. You will obtain faster results by contacting the TAC directly. Workarounds In lieu of an upgrade, the threat may be eliminated or reduced by taking any of the following measures: * Select and configure strong passwords on networking devices. Or * Disable the HTTP server using the command no ip http server while in global configuration mode. Or * If the HTTP server must remain enabled while unrepaired, network access to it can be controlled by applying a standard access list to the HTTP service itself. For example, if the router's HTTP service should be reachable only from a browser running on a computer at IP address 10.1.2.3, then use the following commands in global configuration mode to create a standard access list and apply it to the HTTP server: access-list 1 permit 10.1.2.3 ip http access-class 1 If access list 1 is already in use, then choose another number in the range 0-99. The implicit deny rule added to the end of every access list will prevent access from other IP addresses. Or * Prevent network access to a vulnerable HTTP server by blocking traffic in the network path to the server's port with an extended access list. Such a list would be applied on an interface of the vulnerable router itself or on another Cisco router in the path of a potential attack, e.g., applied inbound on the outside interface of an edge router. The port number used in the extended access list statement must be the default port used by the HTTP server, port 80, or equal to whatever value it may have been set via the ip http port command. Use this workaround with great care; it cannot be recommended confidently without knowledge of specific customer network configurations. Save the resulting configuration in memory so that protection of the server is not inadvertently removed after a reload. Exploitation and Public Announcements The Cisco PSIRT was alerted to this issue by CORE SDI, which discovered the issue during routine security audits on equipment. The security audit included a check for common CGI vulnerabilities against a Cisco device without a configured password; the audit attempted to browse to "http:///cgi-bin/source-help?/", which caused the device to crash and reload. The Cisco PSIRT has received no reports of malicious exploitation of this vulnerability. Status of This Notice: INTERIM This is an interim notice. Cisco expects the contents of this report to change. The reader is warned that this notice may contain inaccurate or incomplete information. Although Cisco cannot guarantee the accuracy of all statements in this notice, all of the facts have been checked to the best of our ability. Cisco anticipates issuing monthly updates of this notice until it reaches final status. Distribution This notice will be posted at http://www.cisco.com/warp/public/707/ioshttpserverquery-pub.shtml. In addition to this HTML version on Cisco's worldwide Web site, a text version of this notice will be clear-signed with the Cisco PSIRT PGP key and posted to the following e-mail addresses and Usenet newsgroups: * cust-security-announce@cisco.com * bugtraq@securityfocus.com * firewalls@lists.gnac.net * first-teams@first.org (which includes the CERT/CC) * cisco@spot.colorado.edu * cisco-nsp@puck.nether.net * comp.dcom.sys.cisco * Various internal Cisco mailing lists Any updates to this notice will appear on Cisco's worldwide Web server. The updates may or may not be announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check http://www.cisco.com/warp/public/707/ioshttpserverquery-pub.shtml. for any updates. Revision History +-------------+-----------+---------------------------------------------+ |Revision 1.0 |2000-09-29 |Draft for initial public release 2000-10-11. | +-------------+-----------+---------------------------------------------+ Cisco Product Security Incident Assistance Process The Web page at http://www.cisco.com/warp/public/707/sec_incident_response.shtml describes how to report security vulnerabilities in Cisco products, obtain assistance with security incidents, and register to receive product security information from Cisco Systems, Inc., including instructions for press inquiries regarding Cisco Security Advisories and notices. This advisory is Cisco's official public statement regarding this vulnerability. _________________________________________________________________ This notice is copyright 2000 by Cisco Systems, Inc. This notice may be redistributed freely after the release date given at the top of the text, provided that redistributed copies are complete and unmodified, including all date and version information. _________________________________________________________________ [****** End of Cisco Bulletin ******]

CIAC wishes to acknowledge the contributions of Cisco for the information contained in this bulletin.
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                     http://ciac.llnl.gov
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