# CVE-2026-98244: btrfs: clear free space tree creation state on rebuild failure

> A flaw in the Linux kernel's btrfs filesystem can cause denial of service by skipping delayed reference processing after a failed free space tree rebuild.

- **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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98244, DEBIAN-CVE-2026-98244, GHSA-mg7q-63qp-3hvm, UBUNTU-CVE-2026-98244

## What is CVE-2026-98244?

CVE-2026-98244 is a denial of service vulnerability in Linux, published on 6 Oct 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:

btrfs: clear free space tree creation state on rebuild failure

btrfs_rebuild_free_space_tree() sets BTRFS_FS_CREATING_FREE_SPACE_TREE
before rebuilding the free space tree.  Several error paths return
without clearing this flag.

The transaction restart failure path can leave the flag set on a live
filesystem, causing delayed reference processing to be skipped. Clear it
on all free space tree rebuild failure paths. Keep
BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED set, since a failed rebuild leaves
the free space tree untrusted. Callers must fall back to extent-tree
caching.

## Which versions are affected by CVE-2026-98244?


## How do I fix CVE-2026-98244?

Apply the vendor's patch.

## Is CVE-2026-98244 being exploited?

There is no known exploitation of CVE-2026-98244 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98244 and fix it if it is affected.

What it is: CVE-2026-98244 is a denial of service vulnerability in Linux, published on 6 Oct 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-2026-98244 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-2026-98244/ (Markdown: https://insights.sbomify.com/CVE-2026-98244/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98244
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98244
- OSV: https://osv.dev/vulnerability/CVE-2026-98244

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98244/
Summaries are generated and may contain mistakes; the official description above is the record.