# net/tcp-md5: Fix MAC comparison to be constant-time

CVE record · `CVE-2026-43383`

- **Identifiers:** `CVE-2026-43383`
- **State:** Confirmed
- **Severity:** CVSS 9.4 Critical
- **Critical:** Yes: CVSS 9+
- **CNA:** Linux
- **Weakness (CWE):** [CWE-208](https://cwe.mitre.org/data/definitions/208.html)
- **Tags:** [CWE-208](https://agentprime.io/advisories/tag/cwe-208.md)
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 8 May 2026
- **Updated:** 19 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 8 May 2026, 14:21 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: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before 821c8751fdeecdeecabeb11704dd33439c9e4bbc` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before ff44ec94d4fc8348600a69de0a8fa1102c23bce8` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before 345a9530756528d7ca407663d659c3c40e75c3dd` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before 5d305a95130a8d08b9545e47f1e18d29d59866cb` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before 02669e2a4d207068edce7e8b5fafd85822018ce6` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before ae3831b44f477de048287493e184fc3ff913b624` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before b502e97e29d791ff7a8051f29a414535739be218` (git)
  - affected: `cfb6eeb4c860592edd123fdea908d23c6ad1c7dc to before 46d0d6f50dab706637f4c18a470aac20a21900d3` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `2.6.20`
  - unaffected: `before 2.6.20` (semver)
  - unaffected: `5.10.253 to 5.10.*, inclusive` (semver)
  - unaffected: `5.15.210 to 5.15.*, inclusive` (semver)
  - unaffected: `6.1.167 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.130 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.78 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.19 to 6.18.*, inclusive` (semver)
  - unaffected: `6.19.9 to 6.19.*, inclusive` (semver)
  - unaffected: `7.0 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:** 0.0054, the 45th percentile, on 5 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 8 May 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-43383](https://www.cve.org/CVERecord?id=CVE-2026-43383)
- [NVD: CVE-2026-43383](https://nvd.nist.gov/vuln/detail/CVE-2026-43383)

### References from the CNA

- <https://git.kernel.org/stable/c/821c8751fdeecdeecabeb11704dd33439c9e4bbc>
- <https://git.kernel.org/stable/c/ff44ec94d4fc8348600a69de0a8fa1102c23bce8>
- <https://git.kernel.org/stable/c/345a9530756528d7ca407663d659c3c40e75c3dd>
- <https://git.kernel.org/stable/c/5d305a95130a8d08b9545e47f1e18d29d59866cb>
- <https://git.kernel.org/stable/c/02669e2a4d207068edce7e8b5fafd85822018ce6>
- <https://git.kernel.org/stable/c/ae3831b44f477de048287493e184fc3ff913b624>
- <https://git.kernel.org/stable/c/b502e97e29d791ff7a8051f29a414535739be218>
- <https://git.kernel.org/stable/c/46d0d6f50dab706637f4c18a470aac20a21900d3>

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-2026-43383>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-43383/>. Everything for agents: <https://agentprime.io/llms.txt>.