# CVE-2025-21853: bpf: avoid holding freeze_mutex during mmap operation

> A race condition in the Linux kernel BPF subsystem can cause deadlocks during memory mapping operations, leading to system denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/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:** 12 Mar 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-58487, AZL-58536, BELL-CVE-2025-21853, DEBIAN-CVE-2025-21853, GHSA-xgr9-crfp-4qg4, ROOT-OS-UBUNTU-2204-CVE-2025-21853, ROOT-OS-UBUNTU-2404-CVE-2025-21853, UBUNTU-CVE-2025-21853

## What is CVE-2025-21853?

CVE-2025-21853 is a medium-severity vulnerability in Linux kernel, published on 12 Mar 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:

bpf: avoid holding freeze_mutex during mmap operation

We use map->freeze_mutex to prevent races between map_freeze() and
memory mapping BPF map contents with writable permissions. The way we
naively do this means we'll hold freeze_mutex for entire duration of all
the mm and VMA manipulations, which is completely unnecessary. This can
potentially also lead to deadlocks, as reported by syzbot in [0].

So, instead, hold freeze_mutex only during writeability checks, bump
(proactively) "write active" count for the map, unlock the mutex and
proceed with mmap logic. And only if something went wrong during mmap
logic, then undo that "write active" counter increment.

  [0] https://lore.kernel.org/bpf/678dcbc9.050a0220.303755.0066.GAE@google.com/

## Which versions are affected by CVE-2025-21853?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21853?

Apply the vendor's patch.

## Is CVE-2025-21853 being exploited?

There is no known exploitation of CVE-2025-21853 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-2025-21853 and fix it if it is affected.

What it is: CVE-2025-21853 is a medium-severity vulnerability in Linux kernel, published on 12 Mar 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-2025-21853 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-2025-21853/ (Markdown: https://insights.sbomify.com/CVE-2025-21853/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21853
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21853
- OSV: https://osv.dev/vulnerability/CVE-2025-21853

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21853/
Summaries are generated and may contain mistakes; the official description above is the record.