# CVE-2026-89567: jbd2: bound shrinker scans by examined checkpoint buffers

> A flaw in the Linux kernel jbd2 shrinker allows local attackers to cause soft lockups or RCU stalls by triggering excessive lock hold times during checkpoint buffer scans.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100253, BELL-CVE-2026-89567, DEBIAN-CVE-2026-89567, GHSA-297x-6x5c-99gq, UBUNTU-CVE-2026-89567

## What is CVE-2026-89567?

CVE-2026-89567 is a denial of service vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

jbd2: bound shrinker scans by examined checkpoint buffers

The jbd2 shrinker currently accounts only checkpoint buffers that it
successfully releases against nr_to_scan.  Busy buffers therefore do not
consume the scan budget.

If a checkpoint transaction contains mostly busy buffers, the shrinker
can scan its entire checkpoint list while holding journal->j_list_lock.
Large checkpoint lists can result in excessive lock hold times and leave
other CPUs spinning on j_list_lock, causing soft lockups or RCU stalls.

Pass nr_to_scan into journal_shrink_one_cp_list() and decrement it for
every buffer examined, including busy buffers.  Pass NULL from checkpoint
cleanup paths so their existing full-list behavior is preserved.

This restores the scan-budget semantics that existed before
journal_shrink_one_cp_list() was changed to always scan a complete
checkpoint list.

## Which versions are affected by CVE-2026-89567?


## How do I fix CVE-2026-89567?

Apply the vendor's patch.

## Is CVE-2026-89567 being exploited?

There is no known exploitation of CVE-2026-89567 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89567 and fix it if it is affected.

What it is: CVE-2026-89567 is a denial of service vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89567 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89567/ (Markdown: https://insights.sbomify.com/CVE-2026-89567/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89567
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89567
- OSV: https://osv.dev/vulnerability/CVE-2026-89567

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89567/
Summaries are generated and may contain mistakes; the official description above is the record.