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CVE-2025-21655

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period io_eventfd_do_signal() is invoked from an RCU callback,…

Published Jan 20, 2025CWE-416EPSS 0.25%

Overview

CVE-2025-21655 is a high-severity vulnerability. It was published on January 20, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. 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/eventfd: ensure io_eventfd_signal() defers another RCU period

io_eventfd_do_signal() is invoked from an RCU callback, but when

dropping the reference to the io_ev_fd, it calls io_eventfd_free()

directly if the refcount drops to zero. This isn't correct, as any

potential freeing of the io_ev_fd should be deferred another RCU grace

period.

Just call io_eventfd_put() rather than open-code the dec-and-test and

free, which will correctly defer it another RCU grace period.

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/6b63308c28987c6010b1180c72a6db4df6c68033Refgit.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10Refgit.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7Refgit.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdbRefproject-zero.issues.chromium.org/issues/388499293Reflists.debian.org/debian-lts-announce/2025/03/msg00001.htmlRefcert-portal.siemens.com/productcert/html/ssa-019113.html

How CyberStrike helps

Frequently asked questions

What is CVE-2025-21655?

CVE-2025-21655 is a high-severity vulnerability. It was published on January 20, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21655?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-21655?

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-2025-21655?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-21655 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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