# btrfs: fix extent map leak in NOCOW direct I/O write

CVE record · `CVE-2026-89644`

- **Identifiers:** `CVE-2026-89644`
- **State:** Confirmed
- **Severity:** No CVSS score
- **Critical:** No
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 11 Sept 2026
- **Updated:** 30 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 11 Sept 2026, 19:45 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: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before 8d264d35df981e943171ddc09cd6cc1d38c65e17` (git)
  - affected: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before cb732d302245b14943a5017015fffa8e6db7a6c0` (git)
  - affected: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before b7c873765875645b11503f94c9bae2ca80127375` (git)
  - affected: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2` (git)
  - affected: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before 05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d` (git)
  - affected: `5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af to before 3f950867c307c5413d628a153ac44915bd117ffd` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `4.7`
  - unaffected: `before 4.7` (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: `6.18.50 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

## Machine-written summary

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

> The Linux kernel btrfs code is affected from version 4.7 until the fixed releases. A failed NOCOW direct I/O write can leak an extent map reference on an error path, and the source gives few details on impact or what an attacker would need. Upgrade to 6.1.191, 6.6.160, 6.12.111, 6.18.50, or a later release in those 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:** 0.0017, the 6th 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-2026-89644](https://www.cve.org/CVERecord?id=CVE-2026-89644)
- [NVD: CVE-2026-89644](https://nvd.nist.gov/vuln/detail/CVE-2026-89644)

### References from the CNA

- <https://git.kernel.org/stable/c/8d264d35df981e943171ddc09cd6cc1d38c65e17>
- <https://git.kernel.org/stable/c/cb732d302245b14943a5017015fffa8e6db7a6c0>
- <https://git.kernel.org/stable/c/b7c873765875645b11503f94c9bae2ca80127375>
- <https://git.kernel.org/stable/c/f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2>
- <https://git.kernel.org/stable/c/05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d>
- <https://git.kernel.org/stable/c/3f950867c307c5413d628a153ac44915bd117ffd>

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-2026-89644>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-89644/>. Everything for agents: <https://agentprime.io/llms.txt>.