# CVE-2025-71159: btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()

> A race condition in the Linux kernel's btrfs filesystem can lead to a use-after-free warning and potential system instability.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Jan 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-71159, DEBIAN-CVE-2025-71159, GHSA-h6p2-5h78-3xmh, UBUNTU-CVE-2025-71159

## What is CVE-2025-71159?

CVE-2025-71159 is a critical use after free vulnerability in Linux kernel, published on 23 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()

Previously, btrfs_get_or_create_delayed_node() set the delayed_node's
refcount before acquiring the root->delayed_nodes lock.
Commit e8513c012de7 ("btrfs: implement ref_tracker for delayed_nodes")
moved refcount_set inside the critical section, which means there is
no longer a memory barrier between setting the refcount and setting
btrfs_inode->delayed_node.

Without that barrier, the stores to node->refs and
btrfs_inode->delayed_node may become visible out of order. Another
thread can then read btrfs_inode->delayed_node and attempt to
increment a refcount that hasn't been set yet, leading to a
refcounting bug and a use-after-free warning.

The fix is to move refcount_set back to where it was to take
advantage of the implicit memory barrier provided by lock
acquisition.

Because the allocations now happen outside of the lock's critical
section, they can use GFP_NOFS instead of GFP_ATOMIC.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-71159?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-71159?

Apply the vendor's patch.

## Is CVE-2025-71159 being exploited?

There is no known exploitation of CVE-2025-71159 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71159 and fix it if it is affected.

What it is: CVE-2025-71159 is a critical use after free vulnerability in Linux kernel, published on 23 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-71159 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-71159/ (Markdown: https://insights.sbomify.com/CVE-2025-71159/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71159
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71159
- OSV: https://osv.dev/vulnerability/CVE-2025-71159

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71159/
Summaries are generated and may contain mistakes; the official description above is the record.