Cisco FXOS and NX-OS System Software Authentication, Authorization, and Accounting Denial of Service Vulnerability

A vulnerability in the authentication, authorization, and accounting (AAA) implementation of Cisco Firepower Extensible Operating System (FXOS) and NX-OS System Software could allow an unauthenticated, remote attacker to cause an affected device to reload.

The vulnerability occurs because AAA processes prevent the NX-OS System Manager from receiving keepalive messages when an affected device receives a high rate of login attempts, such as in a brute-force login attack. System memory can run low on the FXOS devices under the same conditions, which could cause the AAA process to unexpectedly restart or cause the device to reload.

An attacker could exploit this vulnerability by performing a brute-force login attack against a device that is configured with AAA security services. A successful exploit could allow the attacker to cause the affected device to reload.

Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

Note: Previous versions of this advisory recommended upgrading the Cisco NX-OS Software Release and configuring the login block-for CLI command to prevent this vulnerability. Cisco has since become aware that the login block-for CLI command may not function as desired in all cases. This does not apply to Cisco FXOS. Please refer to the Details [“#details”] section for additional information.

This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171018-aaavty [“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171018-aaavty”]