A vulnerability in 802.1x function of Cisco IOS Software on the Catalyst 6500 Series Switches could allow an unauthenticated, adjacent attacker to access the network prior to authentication. The vulnerability is due to how the 802.1x packets are handled in the process path. An attacker could exploit this vulnerability by attempting to connect to the network on an 802.1x configured port. A successful exploit could allow the attacker to intermittently obtain access to the network. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190327-c6500
A vulnerability in 802.1x function of Cisco IOS Software on the Catalyst 6500 Series Switches could allow an unauthenticated, adjacent attacker to access the network prior to authentication.
The vulnerability is due to how the 802.1x packets are handled in the process path. An attacker could exploit this vulnerability by attempting to connect to the network on an 802.1x configured port. A successful exploit could allow the attacker to intermittently obtain access to the network.
Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190327-c6500
This vulnerability affects Cisco Catalyst 6500 Series Switches that are running a vulnerable release of Cisco IOS Software if the 802.1x feature is enabled with authentication host-mode being multi-domain, authentication violation being restrict, and in closed authentication mode on a given interface.
For information about which software releases are vulnerable, see the Fixed Software section of this advisory.
Assessing the 802.1x Configuration
To determine whether the 802.1x feature is configured in a manner that makes a device vulnerable, perform the following tasks:
The following shows an example of an AFFECTED configuration:
interface GigabitEthernet1/4/1 switchport switchport switchport access vlan 100 switchport mode access switchport voice vlan 101 authentication event fail action next-method authentication event server dead action authorize voice authentication event server alive action reinitialize authentication host-mode multi-domain authentication order dot1x mab authentication priority dot1x mab authentication port-control auto authentication periodic authentication timer reauthenticate server authentication violation restrict mab dot1x pae authenticator dot1x timeout tx-period 2 spanning-tree portfast edge spanning-tree bpduguard enable
The following shows an example of a NON-AFFECTED configuration:
interface GigabitEthernet1/4/1 switchport switchport switchport access vlan 100 switchport mode access switchport voice vlan 101 authentication event fail action next-method authentication event server dead action authorize voice authentication event server alive action reinitialize authentication host-mode multi-domain authentication open authentication order dot1x mab authentication priority dot1x mab authentication port-control auto authentication periodic authentication timer reauthenticate server authentication violation shutdown mab dot1x pae authenticator dot1x timeout tx-period 2 spanning-tree portfast edge spanning-tree bpduguard enable
To determine which Cisco IOS Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS Software, the system banner displays text similar to Cisco Internetwork Operating System Software or Cisco IOS Software. The banner also displays the installed image name in parentheses, followed by the Cisco IOS Software release number and release name. Some Cisco devices do not support the show version command or may provide different output.
The following example shows the output of the command for a device that is running Cisco IOS Software Release 15.5(2)T1 and has an installed image name of C2951-UNIVERSALK9-M:
Vulmon
Router> show version
Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2015 by Cisco Systems, Inc.
Compiled Mon 22-Jun-15 09:32 by prod_rel_team
.
.
.
For information about the naming and numbering conventions for Cisco IOS Software releases, see the Cisco IOS and NX-OS Software Reference Guide.
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XE Software, Cisco IOS XR Software, or Cisco NX-OS Software.
If the port is also configured with either authentication violation shutdown|protect, this vulnerability would not be exploitable.
For detailed information about affected and fixed software releases, consult the Cisco IOS Software Checker.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
To help customers determine their exposure to vulnerabilities in Cisco IOS Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies any Cisco Security Advisories that impact a specific Cisco IOS Software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).
Customers can use this tool to perform the following tasks:
To determine whether a release is affected by any published Cisco Security Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS Software release-for example, 15.1(4)M2-in the following field:
By default, the Cisco IOS Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, use the Cisco IOS Software Checker on Cisco.com and check the Medium check box in the Impact Rating drop-down list.
The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
This vulnerability was found during the resolution of a Cisco TAC support case.
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.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2019-March-27 |
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