CVE-2017-6666: A vulnerability in the forwarding component of Cisco IOS XR Software for Cisco Network Convergence System (...

Security readout for executives and security teams

This issue affects Cisco NCS 5500 routers running Cisco IOS XR. A user who already has local authenticated access could trigger a failure that stops the router from forwarding traffic across Traffic Engineering tunnels, causing denial of service. The supplied sources indicate routing disruption risk, not remote takeover. Exposure is most likely in organizations operating Cisco NCS 5500 routers with IOS XR release 6.2.11.BASE and Traffic Engineering tunnel use. Risk depends on who has local authenticated access to the router and whether TE tunnels carry important production traffic. Treat as a targeted network availability risk. It should be prioritized for infrastructure teams managing NCS 5500 routing paths, especially where TE tunnels support customer, backbone, or high-availability traffic. Mitigation focus: Identify Cisco NCS 5500 routers and their IOS XR versions.; Prioritize systems running 6.2.11.BASE and using Traffic Engineering tunnels.; Upgrade to a Cisco-listed fixed release where operationally appropriate..

Prepared

Jun 13, 2026, 04:43 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.