CVE-2025-21655

Medium

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.

Package Linux Kernel
Published 2025-01-20
Last modified 2025-11-03
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

4.7

out of 10
Medium
Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-416

CVE-2025-21655 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.1 and later are affected. Fixed in 6.1.125, 6.6.72, 6.12.10, 6.13 and their respective stable series.

Affected from
≥ 6.1
Fixed in
✓ 6.1.125 6.1.x ✓ 6.6.72 6.6.x ✓ 6.12.10 6.12.x ✓ 6.13

References

The following references provide additional information about CVE-2025-21655 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-2025-21655?

    CVE-2025-21655 is a Medium severity Linux kernel vulnerability with a CVSS score of 4.7 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 6.1 onward and has been patched in 6.1.125, 6.6.72, 6.12.10 and others. CVE-2025-21655 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-21655?

    CVE-2025-21655 has a CVSS score of 4.7 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2025-21655?

    Yes — CVE-2025-21655 has been patched. Fixed versions include 6.1.125, 6.6.72, 6.12.10 and others. If you are running Linux kernel 6.1 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-21655 actively exploited?

    No — CVE-2025-21655 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

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