# net: cap advertised IP tunnel headroom

CVE record · `CVE-2026-80978`

- **Identifiers:** `CVE-2026-80978`
- **State:** Confirmed
- **Severity:** CVSS 7.8 High
- **Critical:** No
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 11 Sept 2026
- **Updated:** 19 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 11 Sept 2026, 19:42 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: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before fb889a619723032140f5d983a3a34d25a5a2bed4` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before b160422f8103574425e2834130e169d84c94fa1d` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before d36e75f5669140b66515ad3a176ca6337bd80a5e` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before 84783961cb8bdb36b4f41a02ce43aafc6d52b176` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before bc4e05ae66c9797a0972ac44326e69c5305e0020` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before af0ee8f04bea22cdb331fa3509e17f81b48938ad` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before 9144f2c53a04465a6878172b523f640313c5559e` (git)
  - affected: `1a37e412a0225fcba5587f24c0dfc7636efc8b69 to before 6b222adeb9340306e2ff97127c76117abb9b3df8` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `3.11`
  - unaffected: `before 3.11` (semver)
  - unaffected: `5.10.270 to 5.10.*, inclusive` (semver)
  - unaffected: `5.15.221 to 5.15.*, inclusive` (semver)
  - unaffected: `6.1.188 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.157 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.109 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.50 to 6.18.*, inclusive` (semver)
  - unaffected: `7.2.4 to 7.2.*, inclusive` (semver)
  - unaffected: `7.3 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0013, the 2nd 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 11 Sept 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-80978](https://www.cve.org/CVERecord?id=CVE-2026-80978)
- [NVD: CVE-2026-80978](https://nvd.nist.gov/vuln/detail/CVE-2026-80978)

### References from the CNA

- <https://git.kernel.org/stable/c/fb889a619723032140f5d983a3a34d25a5a2bed4>
- <https://git.kernel.org/stable/c/b160422f8103574425e2834130e169d84c94fa1d>
- <https://git.kernel.org/stable/c/d36e75f5669140b66515ad3a176ca6337bd80a5e>
- <https://git.kernel.org/stable/c/84783961cb8bdb36b4f41a02ce43aafc6d52b176>
- <https://git.kernel.org/stable/c/bc4e05ae66c9797a0972ac44326e69c5305e0020>
- <https://git.kernel.org/stable/c/af0ee8f04bea22cdb331fa3509e17f81b48938ad>
- <https://git.kernel.org/stable/c/9144f2c53a04465a6878172b523f640313c5559e>
- <https://git.kernel.org/stable/c/6b222adeb9340306e2ff97127c76117abb9b3df8>

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-2026-80978>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-80978/>. Everything for agents: <https://agentprime.io/llms.txt>.