---
id: CVE-2025-21655
title: |-
  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 i…
summary: |-
  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 i…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 6.1, < 6.1.125'
  - 'linux_kernel >= 6.2, < 6.6.72'
  - 'linux_kernel >= 6.7, < 6.12.10'
  - linux_kernel = 6.13
patched:
  - linux_kernel 6.12.10
published: '2025-01-20'
updated: '2026-07-14'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21655'
references:
  - url: 'https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://project-zero.issues.chromium.org/issues/388499293'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00253
epssPercentile: 0.1489
ingestedAt: '2026-07-14T13:36:54.904Z'
---

## Overview

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.

## Affected

- `linux_kernel >= 6.1, < 6.1.125`
- `linux_kernel >= 6.2, < 6.6.72`
- `linux_kernel >= 6.7, < 6.12.10`
- `linux_kernel = 6.13`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.12.10`