# CVE-2025-39878: ceph: fix crash after fscrypt_encrypt_pagecache_blocks() error

> A logic error in the Ceph filesystem code causes kernel crashes when encryption errors occur, leading to 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:** 23 Sep 2025
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2025-39878, DEBIAN-CVE-2025-39878, GHSA-wmpp-p439-v4x7, UBUNTU-CVE-2025-39878

## What is CVE-2025-39878?

CVE-2025-39878 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:

ceph: fix crash after fscrypt_encrypt_pagecache_blocks() error

The function move_dirty_folio_in_page_array() was created by commit
ce80b76dd327 ("ceph: introduce ceph_process_folio_batch() method") by
moving code from ceph_writepages_start() to this function.

This new function is supposed to return an error code which is checked
by the caller (now ceph_process_folio_batch()), and on error, the
caller invokes redirty_page_for_writepage() and then breaks from the
loop.

However, the refactoring commit has gone wrong, and it by accident, it
always returns 0 (= success) because it first NULLs the pointer and
then returns PTR_ERR(NULL) which is always 0.  This means errors are
silently ignored, leaving NULL entries in the page array, which may
later crash the kernel.

The simple solution is to call PTR_ERR() before clearing the pointer.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-39878?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39878?

Apply the vendor's patch.

## Is CVE-2025-39878 being exploited?

There is no known exploitation of CVE-2025-39878 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-2025-39878 and fix it if it is affected.

What it is: CVE-2025-39878 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-2025-39878 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-2025-39878/ (Markdown: https://insights.sbomify.com/CVE-2025-39878/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39878
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39878
- OSV: https://osv.dev/vulnerability/CVE-2025-39878

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39878/
Summaries are generated and may contain mistakes; the official description above is the record.