bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie
CVE-2026-80738 · published 3 Sept 2026
How serious is it
- Severity: high, CVSS score 7.3 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-80738?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: 399040847084a69f345e0a52fd62f04654e0fce3 to < 5702e4c259809c760912c477c4ae34e9217bb4d9, 399040847084a69f345e0a52fd62f04654e0fce3 to < b5525e853a2a08a9559adb84b0616025958dc542, 399040847084a69f345e0a52fd62f04654e0fce3 to < 22c2169770ad3b3595690e51caac875178cf496d, 399040847084a69f345e0a52fd62f04654e0fce3 to < 23f682083aa3fbc0c49667818efd6979a8bc5ac2
- Linux Linux: 5.2
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/5702e4c259809c760912c477c4ae34e9217bb4d9
- git.kernel.org/stable/c/b5525e853a2a08a9559adb84b0616025958dc542
- git.kernel.org/stable/c/22c2169770ad3b3595690e51caac875178cf496d
- git.kernel.org/stable/c/23f682083aa3fbc0c49667818efd6979a8bc5ac2
- git.kernel.org/stable/c/31a420a822ff92e2090bd5d65efe8e34e2d6d9b8
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON