CVE-2015-4199: Cisco IOS

High severity, CVSS 7.1. EPSS: 2.1% chance of exploitation in the next 30 days.

Race condition in the IPv6-to-IPv4 functionality in Cisco IOS 15.3S in the Performance Routing Engine (PRE) module on UBR devices allows remote attackers to cause a denial of service (NULL pointer free and module crash) by triggering intermittent connectivity with many IPv6 CPE devices, aka Bug ID CSCug47366.

Affected products

• Cisco IOS: version 15.3s only

Published 2015-06-27. Last modified 2026-06-17.