CVE-2025-39878

Medium

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.

Package Linux Kernel
Published 2025-09-23
Last modified 2026-01-14
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-476

CVE-2025-39878 is a NULL Pointer Dereference vulnerability

What is NULL Pointer Dereference?

The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.15 and later are affected. Fixed in 6.16.8, 6.17 and their respective stable series.

Affected from
≥ 6.15
Fixed in
✓ 6.16.8 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39878 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Frequently asked questions

  • What is CVE-2025-39878?

    CVE-2025-39878 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as a NULL Pointer Dereference flaw (CWE-476) . It affects Linux kernel versions from 6.15 onward and has been patched in 6.16.8 and 6.17. CVE-2025-39878 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-39878?

    CVE-2025-39878 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2025-39878?

    Yes — CVE-2025-39878 has been patched. Fixed versions include 6.16.8 and 6.17. If you are running Linux kernel 6.15 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-39878 actively exploited?

    No — CVE-2025-39878 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is NULL Pointer Dereference (CWE-476)?

    The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. View CWE-476 on MITRE CWE →

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