CVE-2025-24934 SO_REUSEPORT_LB breaks connect(2) for UDP sockets
Attackers can spoof UDP packets to connected sockets using SO_REUSEPORT_LB, bypassing connection state checks in the FreeBSD kernel.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-24934?
CVE-2025-24934 is a medium-severity vulnerability in FreeBSD, published on 22 Oct 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Software which sets SO_REUSEPORT_LB on a socket and then connects it to a host will not directly observe any problems. However, due to its membership in a load-balancing group, that socket will receive packets originating from any host. This breaks the contract of the connect(2) and implied connect via sendto(2), and may leave the application vulnerable to spoofing attacks.
The kernel failed to check the connection state of sockets when adding them to load-balancing groups. Furthermore, when looking up the destination socket for an incoming packet, the kernel will match a socket belonging to a load-balancing group even if it is connected, in violation of the contract that connected sockets are only supposed to receive packets originating from the connected host.
Weakness: CWE-488
Which versions are affected by CVE-2025-24934?
How do I fix CVE-2025-24934?
No fix has been published for CVE-2025-24934 yet. Limit exposure of the affected software until one is available.
Is CVE-2025-24934 being exploited?
There is no known exploitation of CVE-2025-24934 in the wild and no public exploit code.
Sources
Also known as GHSA-h546-6x4h-w6q7.