# 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.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L`)
- **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:** Yes
- **Published:** 3 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-99072, BELL-CVE-2026-80738, DEBIAN-CVE-2026-80738, GHSA-83j6-pc2m-jhg5, UBUNTU-CVE-2026-80738

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80738 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-80738 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80738/ (Markdown: https://insights.sbomify.com/CVE-2026-80738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80738
- OSV: https://osv.dev/vulnerability/CVE-2026-80738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80738/
Summaries are generated and may contain mistakes; the official description above is the record.