CVE-2024-6640 pf incorrectly matches different ICMPv6 states in the state table
Attackers can bypass pf firewall rules to trigger ICMPv6 Echo Replies by exploiting state table matching flaws in Neighbor Discovery handling.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2024-6640?
CVE-2024-6640 is a medium-severity vulnerability in FreeBSD, published on 11 Aug 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-276
Which versions are affected by CVE-2024-6640?
How do I fix CVE-2024-6640?
No fix has been published for CVE-2024-6640 yet. Limit exposure of the affected software until one is available.
Is CVE-2024-6640 being exploited?
There is no known exploitation of CVE-2024-6640 in the wild and no public exploit code.
Sources
Also known as GHSA-57cg-pmv4-v925.