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Cisco Security Advisory

RADIUS Authentication Bypass

Advisory ID: cisco-sa-20050629-aaa

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050629-aaa

Revision 1.1

Last Updated  2013 February 13 09:01  UTC (GMT)

For Public Release 2005 June 29 16:00  UTC (GMT)


Summary

Remote Authentication Dial In User Service (RADIUS) authentication on a device that is running certain versions of Cisco Internetworking Operating System (IOS) and configured with a fallback method to none can be bypassed.

Systems that are configured for other authentication methods or that are not configured with a fallback method to none are not affected.

Only the systems that are running certain versions of Cisco IOS are affected. Not all configurations using RADIUS and none are vulnerable to this issue. Some configurations using RADIUS, none and an additional method are not affected.

Cisco has made free software available to address this vulnerability. There are workarounds available to mitigate the effects of the vulnerability.

The vulnerabilities are documented as the following Cisco Bug ID:

CSCee45312 -- Radius authentication bypass when configured with a none fallback method.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050629-aaa.

Affected Products

This section provides details on affected products.

Vulnerable Products

Systems that are running the following release trains of Cisco IOS are affected if configured with RADIUS authentication and a none fallback method.

  • 12.2T based trains
  • 12.3 based trains
  • 12.3T based trains
  • 12.4 based trains

A system configured for RADIUS authentication and none fallback method will have a command line in show running-configuration output which is similar to the following .

aaa authentication login xxxxxx group radius none (This is an affected configuration)
aaa authentication ppp xxxxxx group radius none (This is an affected configuration)

A system that is configured for RADIUS authentication with local and none fallback methods is also affected. An example to this configuration may look like similar to the following.

aaa authentication login xxxxxx group radius local none (This is an affected configuration)
aaa authentication ppp xxxxxx group radius local none (This is an affected configuration)

A system is only vulnerable if none method is used as a fallback to RADIUS without any other method in between, or if only local method is used in between. Systems that are configured for RADIUS authentication with a fallback method other than local prior to none method are not affected.

Refer to the Details section for more information about affected and unaffected configurations.

Products Confirmed Not Vulnerable

These products are not vulnerable:

  • Products that are not running Cisco IOS are not affected.
  • Products running Cisco IOS versions 12.1 and earlier (including 12.0S) and 12.2 mainline are not affected.
  • Products that are running Cisco IOS are not affected unless they are configured for RADIUS authentication with a fallback method to none.

No other Cisco products are currently known to be affected by this vulnerability.

Details

Authentication, Authorization, and Accounting (AAA) network security services provide the primary framework through which access control is set up on a device.

AAA authentication services are used to control access to different services on a system. Multiple AAA authentication services can be configured on a system to fall back to a backup authentication method in case the primary authentication method is unavailable.

AAA authentication can be used for different purposes (controlling access to the routers, authenticating remote subscribers etc.).

Refer to the following URL for more information on AAA: http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/fsaaa/index.htm

Remote Authentication Dial In User Service (RADIUS) is defined in RFC2865 and describes a protocol for carrying authentication, authorization, and configuration information.

There is a vulnerability in AAA RADIUS authentication if none is used as a fallback method. Sending a sufficiently long username will bypass the RADIUS authentication and succeed.

Following algorithm can be used to determine whether a configuration is vulnerable:

1. Are you using an affected version of IOS?

No: You are not vulnerable.

Yes: Go to step 2.

2. Is AAA RADIUS Authentication used?

No: You are not vulnerable.

Yes: Go to step 3.

3. Is none used as an alternative to RADIUS?

No: You are not vulnerable.

Yes: Go to step 4.

4. Is there any other method between RADIUS and none?

No: You are vulnerable.

Yes: Go to step 5.

5. Is the other authentication method local?

No: You are not vulnerable.

Yes: Go to step 4.

Based on the algorithm above sample affected and unaffected configurations are given below.

aaa authentication login xxxxxx group radius none (This is an affected configuration)
aaa authentication login xxxxxx group radius local none (This is an affected configuration)
aaa authentication login xxxxxx group radius group tacacs+ none (This is an unaffected configuration)
aaa authentication login xxxxxx group radius enable none (This is an unaffected configuration)
aaa authentication login xxxxxx group radius line none (This is an unaffected configuration)
aaa authentication login xxxxxx group radius local line none (This is an unaffected configuration)

Removing the none fallback method or putting at least one additional method other than local between RADIUS and none will mitigate this vulnerability.

Vulnerability Scoring Details

Cisco has not provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). At the time of original publication, CVSS scoring in Cisco security publications was not yet adopted.

Impact

Successful exploitation of the vulnerability may result in bypassing the RADIUS authentication.

Software Versions and Fixes

When considering software upgrades, please also consult http://www.cisco.com/en/US/products/products_security_advisories_listing.html and any subsequent advisories to determine exposure and a complete upgrade solution.

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. If the information is not clear, contact the Cisco Technical Assistance Center ("TAC") for assistance.

Each row of the Cisco IOS software table (below) describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix (the "First Fixed Release") and the anticipated date of availability for each are listed in the "Rebuild" and "Maintenance" columns. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. The release should be upgraded at least to the indicated release or a later version (greater than or equal to the First Fixed Release label).

For further information on the terms "Rebuild" and "Maintenance, " please consult the following URL: http://www.cisco.com/web/about/security/intelligence/ios-ref.html

Major Release

Availability of Repaired Releases

Affected 12.2-Based Release

Rebuild

Maintenance

12.2B

Vulnerable; migrate to 12.3(11)T or later

12.2BC

Vulnerable; migrate to 12.3(13)BC, available TBD

12.2BW

Vulnerable; migrate to 12.3(10) or later

12.2BX

Vulnerable; migrate to 12.3(7)XI6, available TBD

12.2BY

Vulnerable; migrate to 12.3(11)T or later

12.2BZ

Vulnerable; migrate to 12.3(7)XI6, available TBD

12.2CX

Vulnerable; migrate to 12.3(13)BC, available TBD

12.2CY

Vulnerable; migrate to 12.3(13)BC, available TBD

12.2CZ

Vulnerable; contact TAC

12.2EW

Vulnerable; migrate to 12.2(25)EWA2, available 7-July-05

12.2EWA

12.2(25)EWA2, available 7-July-05

 

12.2EY

12.2(25)EY2

 

12.2EZ

Vulnerable; migrate to 12.2(25)SEC, available 21-July-05

12.2JA

Vulnerable; migrate to 12.3(7)JA, available on 08-Aug-05

12.2JK

Vulnerable; contact TAC

12.2MB

Vulnerable; migrate to 12.2SW

12.2MC

Vulnerable; migrate to 12.3(11)T or later

12.2MX

Vulnerable; migrate to 12.3(11)T or later

12.2SE

12.2(25)SEB2

 
 

12.2(25)SEC, available 21-July-05

12.2SXD

12.2(18)SXD5

 

12.2SXE

12.2(18)SXE2, available 18-July-05

 

12.2T

Vulnerable; migrate to 12.3 train

12.2XB

Vulnerable; migrate to 12.3(10) or later

12.2XC

Vulnerable; migrate to 12.3(11)T or later

12.2XD

Vulnerable; migrate to 12.3(10) or later

12.2XE

Vulnerable; migrate to 12.3(10) or later

12.2XF

Vulnerable; migrate to 12.3(13)BC, available TBD

12.2XG

Vulnerable; migrate to 12.3(10) or later

12.2XH

Vulnerable; migrate to 12.3(10) or later

12.2XI

Vulnerable; migrate to 12.3(10) or later

12.2XJ

Vulnerable; migrate to 12.3(10) or later

12.2XK

Vulnerable; migrate to 12.3(10) or later

12.2XL

Vulnerable; migrate to 12.3(10) or later

12.2XM

Vulnerable; migrate to 12.3(10) or later

12.2XQ

Vulnerable; migrate to 12.3(10) or later

12.2XR/12.2(2)XR/12.2(4)XR

Vulnerable; migrate to 12.3(10) or later

12.2(15)XR

Vulnerable; migrate to 12.3(7)JA, available on 08-Aug-05

12.2XT

Vulnerable; migrate to 12.3(10) or later

12.2XW

Vulnerable; migrate to 12.3(10) or later

12.2YA

Vulnerable; contact TAC

12.2YB

Vulnerable; migrate to 12.3(10) or later

12.2YC

Vulnerable; migrate to 12.3(10) or later

12.2YD

Vulnerable; migrate to 12.3(11)T or later

12.2YF

Vulnerable; migrate to 12.3(10) or later

12.2YG

Vulnerable; migrate to 12.3(10) or later

12.2YH

Vulnerable; migrate to 12.3(10) or later

12.2YJ

Vulnerable; migrate to 12.3(10) or later

12.2YL

Vulnerable; migrate to 12.3(11)T or later

12.2YM

Vulnerable; migrate to 12.3(11)T or later

12.2YN

Vulnerable; migrate to 12.3(11)T or later

12.2YP

Vulnerable; migrate to 12.3(10) or later

12.2YQ

Vulnerable; migrate to 12.3(11)T or later

12.2YR

Vulnerable; migrate to 12.3(11)T or later

12.2YT

Vulnerable; migrate to 12.3(10) or later

12.2YU

Vulnerable; migrate to 12.3(11)T or later

12.2YV

Vulnerable; migrate to 12.3(11)T or later

12.2YW

Vulnerable; migrate to 12.3(11)T or later

12.2YY

Vulnerable; migrate to 12.3(11)T or later

12.2ZB

Vulnerable; migrate to 12.3(11)T or later

12.2ZC

Vulnerable; migrate to 12.3(11)T or later

12.2ZD

Vulnerable; migrate to 12.3(11)T or later

12.2ZE

Vulnerable; migrate to 12.3(10) or later

12.2ZF

Vulnerable; migrate to 12.3(11)T or later

12.2ZG

Vulnerable; migrate to 12.3(11)T or later

12.2ZH

Vulnerable; contact TAC

12.2ZJ

Vulnerable; migrate to 12.3(11)T or later

12.2ZL

Vulnerable; contact TAC

12.2ZN

Vulnerable; migrate to 12.3(11)T or later

12.2ZO

Vulnerable; migrate to 12.3(10) or later

12.2ZP

Vulnerable; migrate to 12.3(11)T or later

Affected 12.3-Based Release

Rebuild

Maintenance

12.3

 

12.3(10)

12.3B

Vulnerable; migrate to 12.3(11)T or later

12.3BC

 

12.3(13)BC, available TBD

12.3BW

Vulnerable; migrate to 12.3(11)T or later

12.3JA

12.3(7)JA, available on 08-Aug-05

12.3T

12.3(7)T11, available TBD

12.3(11)

12.3(8)T4

12.3XA

Vulnerable; migrate to 12.3(11)T or later

12.3XB

Vulnerable; migrate to 12.3(11)T or later

12.3XC

Vulnerable; contact TAC

12.3XD

Vulnerable; migrate to 12.3(11)T or later

12.3XE

Vulnerable; migrate to 12.3(11)T or later

12.3XF

Vulnerable; migrate to 12.3(11)T or later

12.3XG

Vulnerable; migrate to 12.3(11)T or later

12.3XH

Vulnerable; migrate to 12.3(11)T or later

12.3XI

12.3(7)XI6, available TBD

12.3XJ

Vulnerable; migrate to 12.3(11)T or later

12.3XK

Vulnerable; migrate to 12.3(14)T or later

12.3XL

 

12.3(11)XL

12.3XM

Vulnerable; migrate to 12.3(14)T or later

12.3XN

Vulnerable; migrate to 12.3(14)T or later

12.3XQ

Vulnerable; migrate to 12.3(14)T or later

12.3XR

Vulnerable; contact TAC

12.3XS

Vulnerable; migrate to 12.3(14)T or later

12.3XT

Vulnerable; contact TAC

12.3XU

Vulnerable; contact TAC

12.3XW

Vulnerable; migrate to 12.3(11)T or later

12.3XX

Vulnerable; migrate to 12.3(14)T or later

12.3XY

12.3(8)XY5

 

12.3YA

Vulnerable; migrate to 12.3(14)T or later

12.3YB

Vulnerable; contact TAC

12.3YD

 

12.3(8)YD

12.3YF

 

12.3(11)YF

12.3YG

 

12.3(8)YG

12.3YH

 

12.3(8)YH

12.3YI

 

12.3(8)YI

12.3YJ

 

12.3(11)YJ

12.3YK

 

12.3(11)YK

12.3YL

 

12.3(11)YL

12.3YN

 

12.3(11)YN

12.3YR

 

12.3(11)YR

12.3YS

 

12.3(11)YS

12.3YQ

 

12.3(14)YQ

Affected 12.4-Based Release

Rebuild

Maintenance

12.4

 

12.4(1)


Workarounds

The effectiveness of any workaround 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 is the most appropriate for use in the intended network before it is deployed.

  • Removing none as a fallback to RADIUS or putting an additional method other than local between RADIUS and none will mitigate this vulnerability.
    For example, an affected system which has a configuration similar to the following aaa authentication login xxxxxx group radius none can be changed to one of the followingaaa authentication login xxxxxx group radius aaa authentication login xxxxxx group radius enable aaa authentication login xxxxxx group radius enable none aaa authentication login xxxxxx group radius line none as a workaround.

    warning Warning:  Removing none as a fallback method may create problems if the RADIUS server becomes unavailable. With a none fallback in place, all authentication requests will succeed when the RADIUS server is unavailable. Removing none fallback method or replacing it with enable or another mechanism may result in authentication failure if RADIUS server becomes unavailable.

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml .

Do not contact 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 agreements 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 do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire 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

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory. 

Status of This Notice: Final

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.

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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050629-aaa

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 1.1

2005-July-1

Added 12.2XR/12.2(2)XR/12.2(4)XR and 12.2(15)XR to Software Version and Fixes Table. Updated 12.2T row.

Revision 1.0

2005-Jun-29

Initial public release.

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/web/about/security/psirt/security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.


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