-
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.
-
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.
-
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.
-
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: 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.
-
Removing none as a fallback to
RADIUS or putting an additional method other than
local between RADIUS and
none will mitigate this vulnerability.
-
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)
-
The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.
-
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
-
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.
-
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 is an uncontrolled copy, and may lack important information or contain factual errors. The information in this document is intended for end-users of Cisco products.