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CVE-2025-39816

5.5 · 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 p…

Published Sep 16, 2025EPSS 0.15%

Overview

CVE-2025-39816 is a medium-severity vulnerability. It was published on September 16, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/390a61d284e1ced088d43928dfcf6f86fffdd780Refgit.kernel.org/stable/c/695673eb5711ee5eb1769481cf1503714716a7d1Refgit.kernel.org/stable/c/91f262ea2a76a02d9e37dba6637cfe6feebb20a8Refgit.kernel.org/stable/c/98b6fa62c84f2e129161e976a5b9b3cb4ccd117b

How CyberStrike helps

Frequently asked questions

What is CVE-2025-39816?

CVE-2025-39816 is a medium-severity vulnerability. It was published on September 16, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-39816?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-39816?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-39816?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-39816 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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