Cisco NX-OS Software HSRP Authentication Denial of Service Vulnerability

A vulnerability in Hot Standby Router Protocol (HSRP) authentication in the Cisco Nexus series could allow an unauthenticated, adjacent attacker to affect the state of HSRP group members and cause black holing of traffic.

The vulnerability is due to incorrect parsing of malformed HSRP packets. An attacker could exploit this vulnerability by sending malformed HSRP packets to bypass HSRP authentication. An exploit could allow the attacker to bypass HSRP authentication and affect the state of active HSRP group members, causing them to go to SPEAK state, which leads to black holing of traffic and causes a denial of service (DoS) condition.

Cisco has confirmed the vulnerability in a security notice; however, software updates are not available.

Although an attacker does not need to authenticate to a targeted device to exploit this vulnerability, the attacker must be on the same collision or broadcast domain of the targeted device. This access requirement may reduce the likelihood of a successful exploit.

Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.