# CVE-2023-54107: blk-cgroup: dropping parent refcount after pd_free_fn() is done

> A use-after-free vulnerability in the Linux kernel block cgroup subsystem allows attackers to potentially execute code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 24 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2023-54107, DEBIAN-CVE-2023-54107, GHSA-4mrm-9mrj-crwx, ROOT-OS-DEBIAN-12-CVE-2023-54107, ROOT-OS-UBUNTU-2204-CVE-2023-54107, UBUNTU-CVE-2023-54107

## What is CVE-2023-54107?

CVE-2023-54107 is a high-severity use after free vulnerability in Linux, published on 24 Dec 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:

blk-cgroup: dropping parent refcount after pd_free_fn() is done

Some cgroup policies will access parent pd through child pd even
after pd_offline_fn() is done. If pd_free_fn() for parent is called
before child, then UAF can be triggered. Hence it's better to guarantee
the order of pd_free_fn().

Currently refcount of parent blkg is dropped in __blkg_release(), which
is before pd_free_fn() is called in blkg_free_work_fn() while
blkg_free_work_fn() is called asynchronously.

This patch make sure pd_free_fn() called from removing cgroup is ordered
by delaying dropping parent refcount after calling pd_free_fn() for
child.

BTW, pd_free_fn() will also be called from blkcg_deactivate_policy()
from deleting device, and following patches will guarantee the order.

## Which versions are affected by CVE-2023-54107?


## How do I fix CVE-2023-54107?

Apply the vendor's patch.

## Is CVE-2023-54107 being exploited?

There is no known exploitation of CVE-2023-54107 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54107 and fix it if it is affected.

What it is: CVE-2023-54107 is a high-severity use after free vulnerability in Linux, published on 24 Dec 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-2023-54107 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-2023-54107/ (Markdown: https://insights.sbomify.com/CVE-2023-54107/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54107
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54107
- OSV: https://osv.dev/vulnerability/CVE-2023-54107

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54107/
Summaries are generated and may contain mistakes; the official description above is the record.