CVE-1999-1306: Cisco IOS

High severity, CVSS 7.5. EPSS: 1.4% chance of exploitation in the next 30 days.

Cisco IOS 9.1 and earlier does not properly handle extended IP access lists when the IP route cache is enabled and the "established" keyword is set, which could allow attackers to bypass filters.

Affected products

• Cisco IOS: up to and including 9.1

Published 1992-12-10. Last modified 2026-06-16.