# ipv4: validate checksum_start before completing checksum

CVE record · `CVE-2026-99999`

- **Identifiers:** `CVE-2026-99999`
- **State:** Confirmed
- **Severity:** CVSS 9.3 Critical
- **Critical:** Yes: CVSS 9+
- **CNA:** Linux
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html)
- **Tags:** [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md)
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 15 Oct 2026
- **Updated:** 24 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 15 Oct 2026, 12:19 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 9.3: 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: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before a464d950f31c89565cbaae038cc60db04fe01956` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before 0fab003ef4698e0628060a45a48f14b43ba2a40a` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before 94524b7b32691de2e2ce162c04d6cbc9106e5cbf` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before a65f69e0f38ffbed1b128029e09097436416dc8b` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before 32a8b0adaa18e52aaa0b246b5ffe683075354dbb` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before f3e835af6226f1dd12160cbd696081e9b6155de0` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before c3e33464746166264334641dc850a36eef7e6326` (git)
  - affected: `f43798c27684ab925adde7d8acc34c78c6e50df8 to before 6785011f8b16abf40b1e9d8b2e332232b3e68822` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `2.6.27`
  - unaffected: `before 2.6.27` (semver)
  - unaffected: `5.10.272 to 5.10.*, inclusive` (semver)
  - unaffected: `5.15.223 to 5.15.*, inclusive` (semver)
  - unaffected: `6.1.190 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.159 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.113 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.57 to 6.18.*, inclusive` (semver)
  - unaffected: `7.2.11 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0079, the 56th percentile, on 8 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 15 Oct 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-99999](https://www.cve.org/CVERecord?id=CVE-2026-99999)
- [NVD: CVE-2026-99999](https://nvd.nist.gov/vuln/detail/CVE-2026-99999)

### References from the CNA

- <https://git.kernel.org/stable/c/a464d950f31c89565cbaae038cc60db04fe01956>
- <https://git.kernel.org/stable/c/0fab003ef4698e0628060a45a48f14b43ba2a40a>
- <https://git.kernel.org/stable/c/94524b7b32691de2e2ce162c04d6cbc9106e5cbf>
- <https://git.kernel.org/stable/c/a65f69e0f38ffbed1b128029e09097436416dc8b>
- <https://git.kernel.org/stable/c/32a8b0adaa18e52aaa0b246b5ffe683075354dbb>
- <https://git.kernel.org/stable/c/f3e835af6226f1dd12160cbd696081e9b6155de0>
- <https://git.kernel.org/stable/c/c3e33464746166264334641dc850a36eef7e6326>
- <https://git.kernel.org/stable/c/6785011f8b16abf40b1e9d8b2e332232b3e68822>
- <https://pwn.ai/blog/pwnescape>
- <https://vercel.com/blog/findings-from-the-1-million-dollar-vercel-sandbox-challenge>

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-2026-99999>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-99999/>. Everything for agents: <https://agentprime.io/llms.txt>.