CVE-1999-0453: Cisco Router

Medium severity, CVSS 5.0. EPSS: 1.4% chance of exploitation in the next 30 days.

An attacker can identify a CISCO device by sending a SYN packet to port 1999, which is for the Cisco Discovery Protocol (CDP).

Affected products

• Cisco Router: any version

Published 1999-01-01. Last modified 2026-06-16.