# CVE-2025-40241: erofs: fix crafted invalid cases for encoded extents

> Crafted EROFS filesystem images can cause system crashes via out-of-bound access in the Linux kernel, requiring a patch to prevent denial of service.

- **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:** 4 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40241, DEBIAN-CVE-2025-40241, GHSA-9f7m-pc72-73fj, UBUNTU-CVE-2025-40241

## What is CVE-2025-40241?

CVE-2025-40241 is a high-severity denial of service vulnerability in Linux, published on 4 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:

erofs: fix crafted invalid cases for encoded extents

Robert recently reported two corrupted images that can cause system
crashes, which are related to the new encoded extents introduced
in Linux 6.15:

  - The first one [1] has plen != 0 (e.g. plen == 0x2000000) but
    (plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent
    special extents such as sparse extents (!EROFS_MAP_MAPPED), but
    previously only plen == 0 was handled;

  - The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000,
    then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in
    "} while ((cur += bvec.bv_len) < end);" wraps around, causing an
    out-of-bound access of pcl->compressed_bvecs[] in
    z_erofs_submit_queue().  EROFS only supports 48-bit physical block
    addresses (up to 1EiB for 4k blocks), so add a sanity check to
    enforce this.

## Which versions are affected by CVE-2025-40241?


## How do I fix CVE-2025-40241?

Apply the vendor's patch.

## Is CVE-2025-40241 being exploited?

There is no known exploitation of CVE-2025-40241 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40241 and fix it if it is affected.

What it is: CVE-2025-40241 is a high-severity denial of service vulnerability in Linux, published on 4 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-2025-40241 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-2025-40241/ (Markdown: https://insights.sbomify.com/CVE-2025-40241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40241
- OSV: https://osv.dev/vulnerability/CVE-2025-40241

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40241/
Summaries are generated and may contain mistakes; the official description above is the record.