# mptcp: fastopen: only mark MPTFO subflows with SYN data

CVE record · `CVE-2026-80585`

- **Identifiers:** `CVE-2026-80585`
- **State:** Confirmed
- **Severity:** CVSS 9.4 Critical
- **Critical:** Yes: CVSS 9+
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 26 Aug 2026, 14:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Critical

Critical, because:

- CVSS score 9.4: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected products, as the CNA wrote them

- Vendor: Linux. Product: Linux.
  - affected: `36b122baf6a8bd46b4a591f12f4ed17b22257408 to before f75f174edc865738522e514d042cf5627f084859` (git)
  - affected: `36b122baf6a8bd46b4a591f12f4ed17b22257408 to before fca7e444c04689fe4cc6b56f2725f804a4bb1ef9` (git)
  - affected: `36b122baf6a8bd46b4a591f12f4ed17b22257408 to before 75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5` (git)
  - affected: `36b122baf6a8bd46b4a591f12f4ed17b22257408 to before 72b4a0c51a4b550d40301d60a366b429b8c8e78d` (git)
  - affected: `36b122baf6a8bd46b4a591f12f4ed17b22257408 to before e00b63056fb4f261455b3e5df5268a1f8ce47a87` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `6.2`
  - unaffected: `before 6.2` (semver)
  - unaffected: `6.6.153 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.105 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.46 to 6.18.*, inclusive` (semver)
  - unaffected: `7.1.10 to 7.1.*, inclusive` (semver)
  - unaffected: `7.2 to *, inclusive` (original_commit_for_fix)
  - Other versions: affected

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 9.4 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H`, from CNA (Linux)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0031, the 24th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 26 Aug 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-80585](https://www.cve.org/CVERecord?id=CVE-2026-80585)
- [NVD: CVE-2026-80585](https://nvd.nist.gov/vuln/detail/CVE-2026-80585)

### References from the CNA

- <https://git.kernel.org/stable/c/f75f174edc865738522e514d042cf5627f084859>
- <https://git.kernel.org/stable/c/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9>
- <https://git.kernel.org/stable/c/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5>
- <https://git.kernel.org/stable/c/72b4a0c51a4b550d40301d60a366b429b8c8e78d>
- <https://git.kernel.org/stable/c/e00b63056fb4f261455b3e5df5268a1f8ce47a87>

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2026-80585>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-80585/>. Everything for agents: <https://agentprime.io/llms.txt>.