CVE-2026-80738 bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie
A missing state check in Linux kernel BPF TCP syncookie functions allows dereferencing invalid socket fields, potentially causing a kernel crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80738?
CVE-2026-80738 is a high-severity vulnerability in Linux, published on 3 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie
bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie accept a socket pointer 'sk' with argument type ARG_PTR_TO_BTF_ID_SOCK_COMMON. However, they access sk->sk_protocol without validating whether 'sk' represents a full socket.
Fix this issue by checking sk->sk_state != TCP_LISTEN before inspecting sk->sk_protocol in both bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie. Since mini-sockets are never in the TCP_LISTEN state, the condition short-circuits and prevents dereferencing fullsock-specific fields.
Which versions are affected by CVE-2026-80738?
How do I fix CVE-2026-80738?
Apply the vendor's patch.
Is CVE-2026-80738 being exploited?
There is no known exploitation of CVE-2026-80738 in the wild and no public exploit code.
Sources
Also known as AZL-99072, BELL-CVE-2026-80738, DEBIAN-CVE-2026-80738, GHSA-83j6-pc2m-jhg5, UBUNTU-CVE-2026-80738.