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OpenAdvisories
Medium · 5.5 CVE-2025-39816 EUVD-2025-29598GHSA-57pg-f379-59c5

io_uring/kbuf: always use READ_ONCE() to read ring provided buffer lengths

Published Sep 16, 2025 · Updated May 11, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: linux Package: linux-allwinner-5.19 Package: linux-aws-5.0 Package: linux-aws-5.11 Package: linux-aws-5.13 Package: linux-aws-5.19 Package: linux-aws-5.3 Package: linux-aws-5.8 Package: linux-aws-6.14 Package: linux-aws-6.2 Package: linux-aws-6.5 Package: linux-azure Package: linux-azure-5.11 Package: linux-azure-5.13 Package: linux-azure-5.19 Package: linux-azure-5.3 Package: linux-azure-5.8 Package: linux-azure-6.11 Package: linux-azure-6.14 Package: linux-azure-6.2 Package: linux-azure-6.5 Package: linux-azure-edge Package: linux-azure-fde Package: linux-azure-fde-5.19 Package: linux-azure-fde-6.14 Package: linux-azure-fde-6.2 Package: linux-azure-nvidia-6.14 Package: linux-gcp Package: linux-gcp-5.11 Package: linux-gcp-5.13 Package: linux-gcp-5.19 Package: linux-gcp-5.3 Package: linux-gcp-5.8 Package: linux-gcp-6.11 Package: linux-gcp-6.14 Package: linux-gcp-6.2 Package: linux-gcp-6.5 Package: linux-gke Package: linux-gke-4.15 Package: linux-gke-5.15 Package: linux-gke-5.4 Package: linux-gkeop Package: linux-gkeop-5.15 Package: linux-gkeop-5.4 Package: linux-hwe Package: linux-hwe-5.11 Package: linux-hwe-5.13 Package: linux-hwe-5.19 Package: linux-hwe-5.8 Package: linux-hwe-6.11 Package: linux-hwe-6.14 Package: linux-hwe-6.2 Package: linux-hwe-6.5 Package: linux-hwe-edge Package: linux-intel Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-lowlatency-hwe-5.19 Package: linux-lowlatency-hwe-6.11 Package: linux-lowlatency-hwe-6.2 Package: linux-lowlatency-hwe-6.5 Package: linux-nvidia-6.2 Package: linux-nvidia-6.5 Package: linux-oem Package: linux-oem-5.10 Package: linux-oem-5.13 Package: linux-oem-5.14 Package: linux-oem-5.17 Package: linux-oem-5.6 Package: linux-oem-6.0 Package: linux-oem-6.1 Package: linux-oem-6.11 Package: linux-oem-6.14 Package: linux-oem-6.5 Package: linux-oem-6.8 Package: linux-oracle-5.0 Package: linux-oracle-5.11 Package: linux-oracle-5.13 Package: linux-oracle-5.3 Package: linux-oracle-5.8 Package: linux-oracle-6.14 Package: linux-oracle-6.5 Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-realtime-6.14 Package: linux-riscv Package: linux-riscv-5.11 Package: linux-riscv-5.19 Package: linux-riscv-5.8 Package: linux-riscv-6.14 Package: linux-riscv-6.5 Package: linux-starfive-5.19 Package: linux-starfive-6.2 Package: linux-starfive-6.5 Platform: Linux Ecosystem: Debian Ecosystem: Ubuntu

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.

Affected products

VendorProductAffectedFixed
Linux Linux 6.12 6.12.49

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Debian

Security tracker ↗
ReleasePackageFixed inAdvisory
Debian 14 linux 6.16.5-1 —
Debian 13 linux 6.12.57-1 —

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu 25.10 linux-azure-fde No fix yet —
Ubuntu 24.04 LTS linux-intel +18 No fix yet —
Ubuntu 22.04 LTS linux-riscv +32 No fix yet —
Ubuntu 20.04 LTS linux-gke +28 No fix yet —
Ubuntu 18.04 LTS linux-gcp +14 No fix yet —
Show 2 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 No fix yet —

SUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
SLES 15 SP7 kernel-64kb +6 6.4.0-150700.53.19.1 SUSE-SU-2025:03601-1
SLES 15 SP7 kernel-azure +1 6.4.0-150700.20.15.2 SUSE-SU-2025:03633-1
SLES 15 SP7 kernel-default-base 6.4.0-150700.53.19.1.150700.17.13.1 SUSE-SU-2025:03601-1
SLES 15 SP7 kernel-syms-azure 6.4.0-150700.20.15.1 SUSE-SU-2025:03633-1
Show 5 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 kernel-64kb +7 6.12.0-160000.6.1 SUSE-SU-2025:21139-1
SLES for SAP 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21139-1
SLES 16.0 kernel-64kb +7 6.12.0-160000.6.1 SUSE-SU-2025:21179-1, SUSE-SU-2025:21139-1
SLES 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21139-1
SLE Micro 6.2 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21074-1
SLE Micro 6.2 kernel-rt +5 6.12.0-160000.6.1 SUSE-SU-2026:20560-1, SUSE-SU-2025:21074-1
SLE Live Patching 15 SP7 kernel-default 6.4.0-150700.53.19.1 SUSE-SU-2025:03601-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7-RT_Update_5 1-150700.1.3.1 SUSE-SU-2025:3725-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7_Update_5 1-150700.15.3.1 SUSE-SU-2025:03601-1
SUSE Real Time Module 15 SP7 kernel-rt +2 6.4.0-150700.7.19.1 SUSE-SU-2025:3725-1

openSUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
openSUSE Leap 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 openSUSE-SU-2025:20081-1
openSUSE Leap 16.0 kernel-rt +10 6.12.0-160000.6.1 openSUSE-SU-2025:20081-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 kernel-livepatch-6.12.53-69.119 1:1.0-0.amzn2023 ALAS2023-2025-1254
Amazon Linux 2023 perf6.12 +14 1:6.12.53-69.119.amzn2023 ALAS2023-2025-1254

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 9 kernel-uek +34 6.12.0-204.92.4.2.el10uek ELSA-2026-50372

Advisories 11

References