# CVE-2025-39884: btrfs: fix subvolume deletion lockup caused by inodes xarray race

> A race condition in the Linux kernel btrfs filesystem can cause subvolume deletion lockups, leading to system denial of service.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Sep 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-39884, DEBIAN-CVE-2025-39884, GHSA-8f6j-f2h2-wfrj, ROOT-OS-UBUNTU-2204-CVE-2025-39884, ROOT-OS-UBUNTU-2404-CVE-2025-39884, UBUNTU-CVE-2025-39884

## What is CVE-2025-39884?

CVE-2025-39884 is a medium-severity vulnerability in Linux kernel, published on 23 Sep 2025. 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: fix subvolume deletion lockup caused by inodes xarray race

There is a race condition between inode eviction and inode caching that
can cause a live struct btrfs_inode to be missing from the root->inodes
xarray. Specifically, there is a window during evict() between the inode
being unhashed and deleted from the xarray. If btrfs_iget() is called
for the same inode in that window, it will be recreated and inserted
into the xarray, but then eviction will delete the new entry, leaving
nothing in the xarray:

Thread 1                          Thread 2
---------------------------------------------------------------
evict()
  remove_inode_hash()
                                  btrfs_iget_path()
                                    btrfs_iget_locked()
                                    btrfs_read_locked_inode()
                                      btrfs_add_inode_to_root()
  destroy_inode()
    btrfs_destroy_inode()
      btrfs_del_inode_from_root()
        __xa_erase

In turn, this can cause issues for subvolume deletion. Specifically, if
an inode is in this lost state, and all other inodes are evicted, then
btrfs_del_inode_from_root() will call btrfs_add_dead_root() prematurely.
If the lost inode has a delayed_node attached to it, then when
btrfs_clean_one_deleted_snapshot() calls btrfs_kill_all_delayed_nodes(),
it will loop forever because the delayed_nodes xarray will never become
empty (unless memory pressure forces the inode out). We saw this
manifest as soft lockups in production.

Fix it by only deleting the xarray entry if it matches the given inode
(using __xa_cmpxchg()).

Weakness: CWE-667 (Improper Locking)

## Which versions are affected by CVE-2025-39884?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39884?

Apply the vendor's patch.

## Is CVE-2025-39884 being exploited?

There is no known exploitation of CVE-2025-39884 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-2025-39884 and fix it if it is affected.

What it is: CVE-2025-39884 is a medium-severity vulnerability in Linux kernel, published on 23 Sep 2025. 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-2025-39884 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-2025-39884/ (Markdown: https://insights.sbomify.com/CVE-2025-39884/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39884
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39884
- OSV: https://osv.dev/vulnerability/CVE-2025-39884

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39884/
Summaries are generated and may contain mistakes; the official description above is the record.