# CVE-2026-64518: tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

> Out-of-bounds memory access in the Linux kernel TCP stack allows remote attackers to cause denial of service or potentially execute code.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Jul 2026
- **Updated:** 25 Jul 2026
- **Also known as:** BELL-CVE-2026-64518, DEBIAN-CVE-2026-64518, GHSA-mfg2-ph7g-pf6h, ROOT-OS-UBUNTU-2204-CVE-2026-64518, UBUNTU-CVE-2026-64518

## What is CVE-2026-64518?

CVE-2026-64518 is a memory corruption vulnerability in Linux, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

tcp: Fix out-of-bounds access for twsk in tcp_ao_established_key().

lockdep_sock_is_held() was added in tcp_ao_established_key()
by the cited commit.

It can be called from tcp_v[46]_timewait_ack() with twsk.

Since it does not have sk->sk_lock, the lockdep annotation
results in out-of-bound access.

  $ pahole -C tcp_timewait_sock vmlinux | grep size
  	/* size: 288, cachelines: 5, members: 8 */
  $ pahole -C sock vmlinux | grep sk_lock
  	socket_lock_t              sk_lock;              /*   440   192 */

Let's not use lockdep_sock_is_held() for TCP_TIME_WAIT.

## Which versions are affected by CVE-2026-64518?


## How do I fix CVE-2026-64518?

Apply the vendor's patch.

## Is CVE-2026-64518 being exploited?

There is no known exploitation of CVE-2026-64518 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64518 and fix it if it is affected.

What it is: CVE-2026-64518 is a memory corruption vulnerability in Linux, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64518 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-2026-64518/ (Markdown: https://insights.sbomify.com/CVE-2026-64518/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64518
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64518
- OSV: https://osv.dev/vulnerability/CVE-2026-64518

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64518/
Summaries are generated and may contain mistakes; the official description above is the record.