# tcp: clamp route advmss to TCP_MIN_MSS

CVE record · `CVE-2026-80847`

- **Identifiers:** `CVE-2026-80847`
- **State:** Confirmed
- **Severity:** No CVSS score
- **Critical:** No
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 4 Sept 2026
- **Updated:** 30 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 4 Sept 2026, 15:54 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.

## Affected products, as the CNA wrote them

- Vendor: Linux. Product: Linux.
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 1aedef9ca04aad427a077c7c427ffd89768038bc` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 788fbbf7d61f9742298417c207c91b6db159fbbc` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before eaf4af9bd6975c2eff8d48820937c83032d968dc` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before cfb44c6028e6f979720315e0772bbd0d4d33ed61` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 6b8c20bf61924dfc38fefb145c9f7406d73fae53` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 31cf2349361902769dc323e4dbf4b449795ec288` (git)
  - affected: `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to before 870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `2.6.12`
  - unaffected: `before 2.6.12` (semver)
  - unaffected: `6.1.191 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.160 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.111 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.51 to 6.18.*, inclusive` (semver)
  - unaffected: `7.1.13 to 7.1.*, inclusive` (semver)
  - unaffected: `7.2.3 to 7.2.*, inclusive` (semver)
  - unaffected: `7.3 to *, inclusive` (original_commit_for_fix)
  - Other versions: affected

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The Linux kernel TCP stack, from 2.6.12 until fixed, can divide by zero when a route-derived advertised MSS is too small. The source gives few details on attacker requirements. Upgrade to 6.1.191, 6.6.160, 6.12.111, 6.18.51, or a later release in the matching series.

Written 12 Nov 2026.

## 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

No source has published a CVSS score for this record yet.

- **CISA KEV:** Not listed.
- **EPSS:** 0.0021, the 11th percentile, on 14 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 4 Sept 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-80847](https://www.cve.org/CVERecord?id=CVE-2026-80847)
- [NVD: CVE-2026-80847](https://nvd.nist.gov/vuln/detail/CVE-2026-80847)

### References from the CNA

- <https://git.kernel.org/stable/c/1aedef9ca04aad427a077c7c427ffd89768038bc>
- <https://git.kernel.org/stable/c/788fbbf7d61f9742298417c207c91b6db159fbbc>
- <https://git.kernel.org/stable/c/eaf4af9bd6975c2eff8d48820937c83032d968dc>
- <https://git.kernel.org/stable/c/cfb44c6028e6f979720315e0772bbd0d4d33ed61>
- <https://git.kernel.org/stable/c/6b8c20bf61924dfc38fefb145c9f7406d73fae53>
- <https://git.kernel.org/stable/c/31cf2349361902769dc323e4dbf4b449795ec288>
- <https://git.kernel.org/stable/c/870a9e42ecc6fe1b8c25d87af043cb0d9c178fe1>

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-2026-80847>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-80847/>. Everything for agents: <https://agentprime.io/llms.txt>.