[Full-Disclosure] Cisco Security Advisory: SNMP trap Reveals WEP Key in Cisco Aironet AP

2003-12-03T00:00:00
ID SECURITYVULNS:DOC:5479
Type securityvulns
Reporter Securityvulns
Modified 2003-12-03T00:00:00

Description

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Cisco Security Advisory: SNMP trap Reveals WEP Key in Cisco Aironet AP

Revision 1.0

For Public Release 2003 December 02 17:00 UTC (GMT)


Summary

Cisco Aironet Access Points (AP) running Cisco IOS software will send any static Wired Equivalent Privacy (WEP) key in the cleartext to the Simple Network Management Protocol (SNMP) server if the snmp-server enable traps wlan-wep command is enabled. Affected hardware models are the Cisco Aironet 1100, 1200, and 1400 series. This command is disabled by default. The workaround is to disable this command. Any dynamically set WEP key will not be disclosed.

Cisco Aironet AP models running VxWorks operating system are not affected by this vulnerability. No other Cisco product is affected.

This advisory will be available at http://www.cisco.com/warp/public/707/cisco-sa-20031202-SNMP-trap.shtml

Affected Products

Cisco Aironet Access Point 1100, 1200 and 1400 series running Cisco IOS are affected. The Cisco AP 350 running Cisco IOS software is not affected. An Access Points running VxWorks based Operating System are not affected.

To determine if you are running Cisco IOS software, type this command on your workstation, replacing "10.0.0.1" with the IP address of your AP. host%telnet 10.0.0.1

If you are not presented with a menu in a graphic form but simply with a prompt (e.g., ap1200%) then you may be vulnerable.

To further confirm that you are running Cisco IOS software, type the show version command at the prompt. If the result of the command is similar to the example below, then you are running Cisco IOS software. ap1200>show version Cisco Internetwork Operating System Software IOS (tm) C1200 Software (C1200-K9W7-M), Version 12.2(11)JA1, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1) TAC Support: http://www.cisco.com/tac Copyright (c) 1986-2003 by cisco Systems, Inc. Compiled Mon 07-Jul-03 13:48 by ccai Image text-base: 0x00003000, data-base: 0x004D46F4

If you have determined that Cisco IOS software is being used on the AP, execute the following command. ap1200#show running . . . . snmp-server enable traps tty snmp-server enable traps dot11-qos snmp-server enable traps wlan-wep <<<<<< ....

If your configuration contains the line marked with <<, then you are vulnerable.

Details

If enabled, the snmp-server enable traps wlan-wep command will send static WEP keys in cleartext to the SNMP server every time a key is changed or AP rebooted. This vulnerability is opportunistic and, the following conditions must be met for the vulnerability to be exploited.

* A snmp-server enable traps wlan-wep must be enabled. (It is disabled by default.)   * An adversary must be able to intercept SNMP packets sent from the AP to the SNMP server.   * The AP in question must be rebooted or static WEP key changed.

Under these circumstances, an adversary will be able to intercept all static WEP keys.

Dynamically configured WEP keys are not affected by this vulnerability and they will not revealed. A WEP key is dynamically configured if you are using one of the Extensible Authentication Protocol (EAP) authentication protocols. The following EAP protocols are currently supported in Cisco APs: LEAP, EAP-TLS, PEAP, EAP-MD5, and EAP-SIM.

This vulnerability is assigned Cisco bug ID CSCec55538.

Impact

By being able to intercept a static WEP key, an attacker can drastically reduce the effort to break WEP encryption. Please note that this is true only for cases in which you are not using one of the EAP protocols but are using only static WEP keys.

Software Versions and Fixes

The vulnerable IOS releases are: 12.2(8)JA, 12.2(11)JA and 12.2(11)JA1.

The first fixed release is 12.2(13)JA1.

Obtaining Fixed Software

Cisco is offering free software upgrades to remedy this vulnerability for all affected customers. Customers may only install and expect support for the feature sets they have purchased.

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 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 assistance with the upgrade, which should be free of charge.

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). In those cases, customers may only upgrade to a later version of the same release as indicated by the applicable row in the Software Versions and Fixes table. 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)   * email: tac@cisco.com.

See 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.

Please 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.

Please do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades

Workarounds

The workaround is to disable the associated SNMP trap command by typing the following global command: ap1200(config)#no snmp-server enable traps wlan-wep

While the above command will stop the AP from sending your WEP key, Cisco recommends that you do not use static WEP keys but some of the EAP authentication protocols supported by the AP. The WEP scheme itself has several severe drawbacks. For more details regarding wireless LAN security, please see http://www.cisco.com/warp/public/779/smbiz/wireless/wlan_security.shtml/. The papers there are regarding general wireless security and provide configuration examples.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory. This vulnerability was discovered by Bill Van Devender.

Status of This Notice: FINAL

This is a final advisory. Although Cisco cannot guarantee the accuracy of all statements in this advisory, all of the facts have been checked to the best of our ability. Cisco does not anticipate issuing updated versions of this advisory unless there is some material change in the facts. Should there be a significant change in the facts, Cisco will update this advisory.

A stand-alone copy or paraphrase of the text of this security advisory that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.

Distribution

This notice will be posted on Cisco's worldwide website at http://www.cisco.com/warp/public/707/cisco-sa-20031202-SNMP-trap.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 (includes CERT/CC)   * bugtraq@securityfocus.com   * full-disclosure@lists.netsys.com   * vulnwatch@vulnwatch.org   * cisco@spot.colorado.edu   * cisco-nsp@puck.nether.net   * comp.dcom.sys.cisco   * Various internal Cisco mailing lists

Future updates of this notice, if any, will be placed on Cisco's worldwide web Users concerned about this problem are encouraged to check the URL given above for any updates.

Revision History

+---------+-----------+--------------------------------------------+ |Revision |2003-Dec-02|Initial public release. | |1.0 | | | +---------+-----------+--------------------------------------------+

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/warp/public/707/ sec_incident_response.shtml. This includes instructions for press inquiries regarding Cisco security notices. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt.


This notice is Copyright 2003 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, and include all date and version information.


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