# CVE-2026-98245: btrfs: take commit root semaphore when iterating in mark_block_group_to_copy()

> A use-after-free in the Linux kernel btrfs filesystem allows local attackers to execute code or escalate privileges via concurrent transaction commits.

- **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:** 21 Oct 2026
- **Also known as:** AZL-105984, BELL-CVE-2026-98245, DEBIAN-CVE-2026-98245, GHSA-crm6-8p5c-4rv5, UBUNTU-CVE-2026-98245

## What is CVE-2026-98245?

CVE-2026-98245 is an use after free 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: take commit root semaphore when iterating in mark_block_group_to_copy()

mark_block_group_to_copy() iterates over the commit root with
skip_locking=true. A concurrent transaction commit can swap and free
the commit root during iteration, causing use-after-free when
accessing extent buffers.

Fix it by using path->need_commit_sem to protect the commit root search.

## Which versions are affected by CVE-2026-98245?


## How do I fix CVE-2026-98245?

Apply the vendor's patch.

## Is CVE-2026-98245 being exploited?

There is no known exploitation of CVE-2026-98245 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98245 and fix it if it is affected.

What it is: CVE-2026-98245 is an use after free 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-2026-98245 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-2026-98245/ (Markdown: https://insights.sbomify.com/CVE-2026-98245/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98245
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98245
- OSV: https://osv.dev/vulnerability/CVE-2026-98245

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98245/
Summaries are generated and may contain mistakes; the official description above is the record.