# CVE-2026-74270: handshake: Require admin permission for DONE command

> An unprivileged local attacker can forge handshake completion messages to bypass security checks or disrupt legitimate TLS handshakes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74270, DEBIAN-CVE-2026-74270, GHSA-fc6x-h5h8-wjr3, UBUNTU-CVE-2026-74270

## What is CVE-2026-74270?

CVE-2026-74270 is a high-severity missing authorization vulnerability in Linux, published on 15 Aug 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:

handshake: Require admin permission for DONE command

ACCEPT and DONE are the two downcalls of the handshake genl
family, both intended for use by the trusted handshake agent
(tlshd). ACCEPT already requires GENL_ADMIN_PERM; DONE has
no privilege check at all.

The fd-lookup in handshake_nl_done_doit() only confirms that
some pending handshake request exists for the supplied sockfd;
it does not authenticate the sender. An unprivileged process
that guesses or observes a valid sockfd can therefore submit
a DONE with HANDSHAKE_A_DONE_STATUS == 0, leaving the kernel
consumer to proceed as if the handshake succeeded. A non-zero
status on a forged DONE tears down a legitimate in-flight
handshake before tlshd can report its real result.

## Which versions are affected by CVE-2026-74270?


## How do I fix CVE-2026-74270?

Apply the vendor's patch.

## Is CVE-2026-74270 being exploited?

There is no known exploitation of CVE-2026-74270 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74270 and fix it if it is affected.

What it is: CVE-2026-74270 is a high-severity missing authorization vulnerability in Linux, published on 15 Aug 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-2026-74270 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-2026-74270/ (Markdown: https://insights.sbomify.com/CVE-2026-74270/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74270
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74270
- OSV: https://osv.dev/vulnerability/CVE-2026-74270

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74270/
Summaries are generated and may contain mistakes; the official description above is the record.