Summary
In the Linux kernel, the following vulnerability has been resolved: io_uring/kbuf: always use...
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.
Impact
CVE-2025-39816 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Frequently Asked Questions
- What is CVE-2025-39816? CVE-2025-39816 is a medium-severity security vulnerability. No fixed version is listed yet.
- How severe is CVE-2025-39816? CVE-2025-39816 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Is there a fix for CVE-2025-39816? No fixed version is listed for CVE-2025-39816 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-39816 exploitable, and should I be worried? Whether CVE-2025-39816 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-39816 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.