# f2fs: avoid NULL checkpoint thread access in sysfs

CVE record · `CVE-2026-89835`

- **Identifiers:** `CVE-2026-89835`
- **State:** Confirmed
- **Severity:** No CVSS score
- **Critical:** No
- **CNA:** Linux
- **Technologies:** [Linux kernel](https://agentprime.io/advisories/technology/linux-kernel.md)
- **Published:** 16 Sept 2026
- **Updated:** 30 Oct 2026
- **Reviewed by a person:** No

Published by the CVE Program (CNA: Linux) at 16 Sept 2026, 10:31 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: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before 54196bcfde998fb37009f50e0ef16498f651f0f9` (git)
  - affected: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before 22760e3e9cecbddc475edc91600787abf407a302` (git)
  - affected: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before a6573f3ffc19542de9ebc1a2b1f930fd48ba538c` (git)
  - affected: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before aefcec3bebdeed2bff444378122300763325ba23` (git)
  - affected: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before 8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b` (git)
  - affected: `e65920661708b7c0f3db45c9cd5d0095034ee37f to before 5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f` (git)
  - Other versions: unaffected
- Vendor: Linux. Product: Linux.
  - affected: `5.12`
  - unaffected: `before 5.12` (semver)
  - unaffected: `6.1.191 to 6.1.*, inclusive` (semver)
  - unaffected: `6.6.160 to 6.6.*, inclusive` (semver)
  - unaffected: `6.12.110 to 6.12.*, inclusive` (semver)
  - unaffected: `6.18.51 to 6.18.*, inclusive` (semver)
  - unaffected: `7.2.5 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's f2fs filesystem, in versions from commit e65920661708 up to the fixes listed for this CVE, can dereference a NULL checkpoint thread pointer when the ckpt_thread_ioprio sysfs file is written. This happens when checkpoint_merge is enabled without a running checkpoint thread, such as on a read-only mount. The source gives few details on the attacker's position. Upgrade to a fixed kernel version: 5.12 and later are affected, and fixes are listed for the 6.1, 6.6, 6.12 and 6.18 stable branches. No other workaround is listed.

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:** 0.0022, 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 16 Sept 2026. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2026-89835](https://www.cve.org/CVERecord?id=CVE-2026-89835)
- [NVD: CVE-2026-89835](https://nvd.nist.gov/vuln/detail/CVE-2026-89835)

### References from the CNA

- <https://git.kernel.org/stable/c/54196bcfde998fb37009f50e0ef16498f651f0f9>
- <https://git.kernel.org/stable/c/22760e3e9cecbddc475edc91600787abf407a302>
- <https://git.kernel.org/stable/c/a6573f3ffc19542de9ebc1a2b1f930fd48ba538c>
- <https://git.kernel.org/stable/c/aefcec3bebdeed2bff444378122300763325ba23>
- <https://git.kernel.org/stable/c/8f3b99c50dd0da1777994ce7c7e60d39b9f60f4b>
- <https://git.kernel.org/stable/c/5cb33b00c8fbb6e8f1fa3d281c3036d5f7c7c41f>

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-2026-89835>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2026-89835/>. Everything for agents: <https://agentprime.io/llms.txt>.