CVE-2019-1977: Cisco NX-OS

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

A vulnerability within the Endpoint Learning feature of Cisco Nexus 9000 Series Switches running in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an endpoint device in certain circumstances. The vulnerability is due to improper endpoint learning when packets are received on a specific port from outside the ACI fabric and destined to an endpoint located on a border leaf when Disable Remote Endpoint Learning has been enabled. This can result in a Remote (XR) entry being created for the impacted endpoint that will become stale if the endpoint migrates to a different port or leaf switch. This results in traffic not reaching the impacted endpoint until the Remote entry can be relearned by another mechanism.

Affected products

• Cisco NX-OS: version 12.3(1h) only; version 13.1(2m) only; version 13.1(2o) only; version 13.1(2p) only

Published 2019-08-30. Last modified 2026-06-17.