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. This vulnerability affects the following Cisco products if they are running Cisco FXOS or NX-OS System Software that is configured for AAA services: Firepower 4100 Series Next-Generation Firewall, Firepower 9300 Security Appliance, Multilayer Director Switches, Nexus 1000V Series Switches, Nexus 1100 Series Cloud Services Platforms, Nexus 2000 Series Switches, Nexus 3000 Series Switches, Nexus 3500 Platform Switches, Nexus 5000 Series Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, Nexus 7000 Series Switches, Nexus 7700 Series Switches, Nexus 9000 Series Switches in NX-OS mode, Nexus 9500 R-Series Line Cards and Fabric Modules, Unified Computing System (UCS) 6100 Series Fabric Interconnects, UCS 6200 Series Fabric Interconnects, UCS 6300 Series Fabric Interconnects. Cisco Bug IDs: CSCuq58760, CSCuq71257, CSCur97432, CSCus05214, CSCux54898, CSCvc33141, CSCvd36971, CSCve03660.