CVE-2025-39899

Medium

In the Linux kernel, the following vulnerability has been resolved: mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using kmap_local_page(), which requires unmapping in Last-In-First-Out order. The current code maps dst_pte first, then src_pte, but unmaps them in the same order (dst_pte, src_pte), violating the LIFO requirement. This causes the warning in kunmap_local_indexed(): WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx) Fix this by reversing the unmap order to respect LIFO ordering. This issue follows the same pattern as similar fixes: - commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order") - commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename") Both of which addressed the same fundamental requirement that kmap_local operations must follow LIFO ordering.

Package Linux Kernel
Published 2025-10-01
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

Affected versions

Linux kernel versions 6.8 and later are affected. Fixed in 6.12.46, 6.16.6, 6.17 and their respective stable series.

Affected from
≥ 6.8
Fixed in
✓ 6.12.46 6.12.x ✓ 6.16.6 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39899 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-2025-39899?

    CVE-2025-39899 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 6.8 onward and has been patched in 6.12.46, 6.16.6 and 6.17. CVE-2025-39899 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-39899?

    CVE-2025-39899 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-2025-39899?

    Yes — CVE-2025-39899 has been patched. Fixed versions include 6.12.46, 6.16.6 and 6.17. If you are running Linux kernel 6.8 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-39899 actively exploited?

    No — CVE-2025-39899 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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