CVE-2025-39816

Medium

In the Linux kernel, the following vulnerability has been resolved: io_uring/kbuf: always use READ_ONCE() to read ring provided buffer lengths Since the buffers are mapped from userspace, it is prudent to use READ_ONCE() to read the value into a local variable, and use that for any other actions taken. Having a stable read of the buffer length avoids worrying about it changing after checking, or being read multiple times. Similarly, the buffer may well change in between it being picked and being committed. Ensure the looping for incremental ring buffer commit stops if it hits a zero sized buffer, as no further progress can be made at that point.

Package Linux Kernel
Published 2025-09-16
Last modified 2026-04-11
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 6.12 and later are affected. Fixed in 6.12.49, 6.12.81, 6.16.5, 6.17 and their respective stable series.

Affected from
≥ 6.12
Fixed in
✓ 6.12.49 6.12.x ✓ 6.12.81 6.12.x ✓ 6.16.5 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39816 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

4 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2025-39816?

    CVE-2025-39816 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 6.12 onward and has been patched in 6.12.49, 6.12.81, 6.16.5 and others. CVE-2025-39816 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-39816?

    CVE-2025-39816 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-2025-39816?

    Yes — CVE-2025-39816 has been patched. Fixed versions include 6.12.49, 6.12.81, 6.16.5 and others. If you are running Linux kernel 6.12 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-39816 actively exploited?

    No — CVE-2025-39816 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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