Cisco Nexus 1000V Switch for VMware vSphere Secure Login Enhancements Denial of Service Vulnerability

Vulnerability

A denial of service (DoS) vulnerability exists in the Secure Login Enhancements capability of Cisco Nexus 1000V Switch for VMware vSphere (Virtual Supervisor Module, VSM). The flaw stems from improper resource allocation during failed CLI login attempts when certain login parameters from Secure Login Enhancements are configured. Affected versions include Cisco NX-OS Software releases prior to the fixed versions indicated in the Cisco advisory [1].

Exploitation

An unauthenticated, remote attacker can exploit the vulnerability by sending a high volume of login attempts to the affected device. No authentication or prior access is required. The attacker needs only network connectivity to the VSM's management interface; the device does not need to have any other vulnerabilities or configurations beyond the Secure Login Enhancements feature being enabled [1].

Impact

Successful exploitation exhausts resources on the VSM, causing it to become inaccessible to legitimate users through the CLI. This leads to a denial of service condition that requires a manual power cycle of the VSM to restore normal operation. The attack does not grant any data access or code execution; it solely impairs availability [1].

Mitigation

Cisco has released free software updates that address this vulnerability. Customers should upgrade to a fixed NX-OS software version as specified in the Cisco Security Advisory [1]. No workaround is available. If a manual power cycle must be performed temporarily, users should contact Cisco TAC for guidance. The vulnerability is not listed on the CISA KEV catalog.