# CVE-2025-38579: f2fs: fix KMSAN uninit-value in extent_info usage

> A local attacker can read uninitialized kernel memory via the f2fs filesystem, potentially exposing sensitive data.

- **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:** 19 Aug 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-38579, DEBIAN-CVE-2025-38579, GHSA-6x6v-877j-v9fv, ROOT-OS-DEBIAN-12-CVE-2025-38579, ROOT-OS-DEBIAN-13-CVE-2025-38579, ROOT-OS-UBUNTU-2204-CVE-2025-38579, ROOT-OS-UBUNTU-2404-CVE-2025-38579, UBUNTU-CVE-2025-38579

## What is CVE-2025-38579?

CVE-2025-38579 is a high-severity vulnerability in Debian Debian Linux, published on 19 Aug 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:

f2fs: fix KMSAN uninit-value in extent_info usage

KMSAN reported a use of uninitialized value in `__is_extent_mergeable()`
 and `__is_back_mergeable()` via the read extent tree path.

The root cause is that `get_read_extent_info()` only initializes three
fields (`fofs`, `blk`, `len`) of `struct extent_info`, leaving the
remaining fields uninitialized. This leads to undefined behavior
when those fields are accessed later, especially during
extent merging.

Fix it by zero-initializing the `extent_info` struct before population.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2025-38579?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38579?

Apply the vendor's patch.

## Is CVE-2025-38579 being exploited?

There is no known exploitation of CVE-2025-38579 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38579 and fix it if it is affected.

What it is: CVE-2025-38579 is a high-severity vulnerability in Debian Debian Linux, published on 19 Aug 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-2025-38579 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38579/ (Markdown: https://insights.sbomify.com/CVE-2025-38579/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38579
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38579
- OSV: https://osv.dev/vulnerability/CVE-2025-38579

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38579/
Summaries are generated and may contain mistakes; the official description above is the record.