CVE-1999-0063: Cisco IOS

Medium severity, CVSS 5.0. EPSS: 8.2% chance of exploitation in the next 30 days.

Cisco IOS 12.0 and other versions can be crashed by malicious UDP packets to the syslog port.

Affected products

• Cisco IOS: version 11.3aa only; version 11.3db only; version 12.0 only; version 12.0(1)w only; version 12.0(1)xa3 only; version 12.0(1)xb only; …

Published 1999-01-11. Last modified 2026-06-16.