CVE-2021-1231: Cisco NX-OS

Medium severity, CVSS 4.7. EPSS: 0.3% chance of exploitation in the next 30 days.

A vulnerability in the Link Layer Discovery Protocol (LLDP) for Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, adjacent attacker to disable switching on a small form-factor pluggable (SFP) interface. This vulnerability is due to incomplete validation of the source of a received LLDP packet. An attacker could exploit this vulnerability by sending a crafted LLDP packet on an SFP interface to an affected device. A successful exploit could allow the attacker to disable switching on the SFP interface, which could disrupt network traffic.

Affected products

• Cisco NX-OS: version 11.0(1b) only; version 11.0(1c) only; version 11.0(1d) only; version 11.0(1e) only; version 11.0(2j) only; version 11.0(2m) only; …

Published 2021-02-24. Last modified 2026-06-17.