CVE-2024-6640: Freebsd

Medium severity, CVSS 6.3. EPSS: 0.5% chance of exploitation in the next 30 days.

In ICMPv6 Neighbor Discovery (ND), the ID is always 0. When pf is configured to allow ND and block incoming Echo Requests, a crafted Echo Request packet after a Neighbor Solicitation (NS) can trigger an Echo Reply. The packet has to come from the same host as the NS and have a zero as identifier to match the state created by the Neighbor Discovery and allow replies to be generated. ICMPv6 packets with identifier value of zero bypass firewall rules written on the assumption that the incoming packets are going to create a state in the state table.

Affected products

• Freebsd Freebsd: from 14.1-RELEASE, before p3 (fixed in p3); from 14.0-RELEASE, before p9 (fixed in p9); from 13.3-RELEASE, before p5 (fixed in p5)

Published 2024-08-12. Last modified 2026-06-17.