Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-64034

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Main Vulnerability Database Vulnerabilities #VU138612

Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-64034

Published: July 20, 2026


Vulnerability identifier: #VU138612
CSH Severity: Low
CVSS v4: 2.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64034
CWE-ID: CWE-367
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass bounds validation.

The vulnerability exists due to a time-of-check time-of-use double-fetch in mana_hwc_rx_event_handler() and mana_hwc_handle_resp() when reading hwc_msg_id from a DMA-coherent buffer. A remote attacker can modify the DMA-visible hwc_msg_id value between reads to bypass bounds validation.

Exploitation requires hardware or a host environment able to alter shared, unencrypted DMA-coherent memory between the check and the subsequent use, such as in confidential VM environments.


Affected software

Linux kernel
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Micro
SUSE Linux Micro Extras
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat CodeReady Linux Builder for x86_64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for ARM 64
SUSE Linux Enterprise Live Patching
Basesystem Module
Development Tools Module
Legacy Module
Public Cloud Module
SUSE Real Time Module
openSUSE Leap
Ubuntu
kernel-livepatch-SLE15-SP6_Update_31-debugsource
kernel-livepatch-6_4_0-150600_23_135-default-debuginfo
kernel-livepatch-6_4_0-150600_23_135-default
kernel-livepatch-6_4_0-150700_7_75-rt-debuginfo
kernel-livepatch-6_4_0-150700_7_75-rt
kernel-livepatch-SLE15-SP7-RT_Update_20-debugsource
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo
kernel-livepatch-6_4_0-150700_53_81-default
kernel-livepatch-SLE15-SP7_Update_21-debugsource
kernel (Red Hat package)
kernel-rt (Red Hat package)
kernel-rt-livepatch
kernel-default
kernel-64kb
kernel-64kb-debugsource
kernel-64kb-devel
kernel-obs-build
kernel-syms
kernel-default-devel
kernel-default-debugsource
kernel-rt-debugsource
kernel-devel
kernel-kvmsmall
kernel-obs-build-debugsource
kernel-source-rt
kernel-devel-rt
kernel-rt
kernel-rt-debuginfo
kernel-macros
kernel-source
kernel-default-livepatch
kernel-default-debuginfo
kernel-kvmsmall-debugsource
kernel-kvmsmall-debuginfo
kernel-default-devel-debuginfo
kernel-default-base
reiserfs-kmp-64kb-debuginfo
kernel-docs
kernel-default-livepatch-devel
reiserfs-kmp-64kb
kernel-64kb-devel-debuginfo
gfs2-kmp-64kb
kselftests-kmp-64kb-debuginfo
kernel-64kb-debuginfo
dlm-kmp-64kb-debuginfo
ocfs2-kmp-64kb-debuginfo
dlm-kmp-64kb
cluster-md-kmp-64kb
ocfs2-kmp-default
cluster-md-kmp-default-debuginfo
gfs2-kmp-default
ocfs2-kmp-default-debuginfo
gfs2-kmp-default-debuginfo
dlm-kmp-default-debuginfo
reiserfs-kmp-default-debuginfo
dlm-kmp-default
cluster-md-kmp-default
reiserfs-kmp-default
kernel-kvmsmall-devel
kernel-debug-debugsource
kernel-debug-devel
kernel-debug-debuginfo
kernel-kvmsmall-vdso-debuginfo
kernel-debug-vdso-debuginfo
kernel-kvmsmall-vdso
kernel-default-vdso
kernel-default-vdso-debuginfo
kernel-debug-vdso
cluster-md-kmp-64kb-debuginfo
kernel-kvmsmall-devel-debuginfo
kernel-docs-html
kernel-source-vanilla
kernel-zfcpdump
kernel-zfcpdump-debuginfo
kernel-zfcpdump-debugsource
kernel-debug-devel-debuginfo
kernel-64kb-extra
kernel-64kb-extra-debuginfo
ocfs2-kmp-64kb
kselftests-kmp-64kb
kernel-64kb-optional-debuginfo
gfs2-kmp-64kb-debuginfo
kernel-64kb-optional
kselftests-kmp-default
kernel-default-optional
kernel-default-extra
kselftests-kmp-default-debuginfo
kernel-default-optional-debuginfo
kernel-obs-qa
kernel-default-extra-debuginfo
kernel-debug
kernel-default-base-rebuild
ocfs2-kmp-rt
cluster-md-kmp-rt-debuginfo
dlm-kmp-rt-debuginfo
gfs2-kmp-rt
ocfs2-kmp-rt-debuginfo
kernel-rt-devel-debuginfo
cluster-md-kmp-rt
kernel-rt-devel
dlm-kmp-rt
gfs2-kmp-rt-debuginfo
kernel-syms-rt
kernel-azure-debugsource
kernel-azure-debuginfo
kernel-azure-devel-debuginfo
kernel-azure-devel
kernel-azure
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-nvidia-tegra-5.15 (Ubuntu package)
linux-intel-iot-realtime (Ubuntu package)
linux-raspi (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-azure (Ubuntu package)
linux-gcp-5.15 (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-gcp-6.8 (Ubuntu package)
linux-oracle (Ubuntu package)
linux-azure-fde-6.8 (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-raspi-realtime (Ubuntu package)
linux-azure-fde-6.17 (Ubuntu package)
linux-azure-6.17 (Ubuntu package)
linux-ibm (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

How to mitigate CVE-2026-64034

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel-livepatch-SLE15-SP6_Update_31-debugsource - update to 1-150600.13.3.4
kernel-livepatch-6_4_0-150600_23_135-default-debuginfo - update to 1-150600.13.3.4
kernel-livepatch-6_4_0-150600_23_135-default - update to 1-150600.13.3.4
kernel-livepatch-6_4_0-150700_7_75-rt-debuginfo - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_7_75-rt - update to 1-150700.1.3.1
kernel-livepatch-SLE15-SP7-RT_Update_20-debugsource - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo - update to 1-150700.15.3.1
kernel-livepatch-6_4_0-150700_53_81-default - update to 1-150700.15.3.1
kernel-livepatch-SLE15-SP7_Update_21-debugsource - update to 1-150700.15.3.1
kernel (Red Hat package) - update to 4.18.0-553.169.1.el8_10
kernel-rt (Red Hat package) - update to 4.18.0-553.169.1.rt7.510.el8_10
kernel-rt-livepatch - update to 6.4.0-52.1
kernel-default - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-64kb - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-64kb-debugsource - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-64kb-devel - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-obs-build - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-syms - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-devel - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-debugsource - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-rt-debugsource - addressed in versions 6.4.0-52.1, 6.4.0-150700.7.75.1
kernel-devel - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-kvmsmall - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1
kernel-obs-build-debugsource - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-source-rt - addressed in versions 6.4.0-52.1, 6.4.0-150700.7.75.1
kernel-devel-rt - addressed in versions 6.4.0-52.1, 6.4.0-150700.7.75.1
kernel-rt - addressed in versions 6.4.0-52.1, 6.4.0-150700.7.75.1
kernel-rt-debuginfo - addressed in versions 6.4.0-52.1, 6.4.0-150700.7.75.1
kernel-macros - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-source - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-livepatch - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-debuginfo - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-kvmsmall-debugsource - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1
kernel-kvmsmall-debuginfo - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1
kernel-default-devel-debuginfo - addressed in versions 6.4.0-52.1, 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-base - addressed in versions 6.4.0-52.1.21.35, 6.4.0-52.1.21.36, 6.4.0-150600.23.135.1.150600.12.62.4, 6.4.0-150700.53.81.1.150700.17.45.1
reiserfs-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
kernel-docs - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-default-livepatch-devel - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
reiserfs-kmp-64kb - update to 6.4.0-150600.23.135.1
kernel-64kb-devel-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
gfs2-kmp-64kb - update to 6.4.0-150600.23.135.1
kselftests-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
kernel-64kb-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
dlm-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
ocfs2-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
dlm-kmp-64kb - update to 6.4.0-150600.23.135.1
cluster-md-kmp-64kb - update to 6.4.0-150600.23.135.1
ocfs2-kmp-default - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
cluster-md-kmp-default-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
gfs2-kmp-default - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
ocfs2-kmp-default-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
gfs2-kmp-default-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
dlm-kmp-default-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
reiserfs-kmp-default-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
dlm-kmp-default - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
cluster-md-kmp-default - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
reiserfs-kmp-default - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-kvmsmall-devel - update to 6.4.0-150600.23.135.1
kernel-debug-debugsource - update to 6.4.0-150600.23.135.1
kernel-debug-devel - update to 6.4.0-150600.23.135.1
kernel-debug-debuginfo - update to 6.4.0-150600.23.135.1
kernel-kvmsmall-vdso-debuginfo - update to 6.4.0-150600.23.135.1
kernel-debug-vdso-debuginfo - update to 6.4.0-150600.23.135.1
kernel-kvmsmall-vdso - update to 6.4.0-150600.23.135.1
kernel-default-vdso - update to 6.4.0-150600.23.135.1
kernel-default-vdso-debuginfo - update to 6.4.0-150600.23.135.1
kernel-debug-vdso - update to 6.4.0-150600.23.135.1
cluster-md-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
kernel-kvmsmall-devel-debuginfo - update to 6.4.0-150600.23.135.1
kernel-docs-html - update to 6.4.0-150600.23.135.1
kernel-source-vanilla - update to 6.4.0-150600.23.135.1
kernel-zfcpdump - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-zfcpdump-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-zfcpdump-debugsource - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-debug-devel-debuginfo - update to 6.4.0-150600.23.135.1
kernel-64kb-extra - update to 6.4.0-150600.23.135.1
kernel-64kb-extra-debuginfo - update to 6.4.0-150600.23.135.1
ocfs2-kmp-64kb - update to 6.4.0-150600.23.135.1
kselftests-kmp-64kb - update to 6.4.0-150600.23.135.1
kernel-64kb-optional-debuginfo - update to 6.4.0-150600.23.135.1
gfs2-kmp-64kb-debuginfo - update to 6.4.0-150600.23.135.1
kernel-64kb-optional - update to 6.4.0-150600.23.135.1
kselftests-kmp-default - update to 6.4.0-150600.23.135.1
kernel-default-optional - update to 6.4.0-150600.23.135.1
kernel-default-extra - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kselftests-kmp-default-debuginfo - update to 6.4.0-150600.23.135.1
kernel-default-optional-debuginfo - update to 6.4.0-150600.23.135.1
kernel-obs-qa - update to 6.4.0-150600.23.135.1
kernel-default-extra-debuginfo - addressed in versions 6.4.0-150600.23.135.1, 6.4.0-150700.53.81.1
kernel-debug - update to 6.4.0-150600.23.135.1
kernel-default-base-rebuild - update to 6.4.0-150600.23.135.1.150600.12.62.4
ocfs2-kmp-rt - update to 6.4.0-150700.7.75.1
cluster-md-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
dlm-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
gfs2-kmp-rt - update to 6.4.0-150700.7.75.1
ocfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
kernel-rt-devel-debuginfo - update to 6.4.0-150700.7.75.1
cluster-md-kmp-rt - update to 6.4.0-150700.7.75.1
kernel-rt-devel - update to 6.4.0-150700.7.75.1
dlm-kmp-rt - update to 6.4.0-150700.7.75.1
gfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
kernel-syms-rt - update to 6.4.0-150700.7.75.1
kernel-azure-debugsource - update to 6.4.0-150700.53.81.1
kernel-azure-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-devel - update to 6.4.0-150700.53.81.1
kernel-azure - update to 6.4.0-150700.53.81.1
linux (Ubuntu package) - addressed in versions 5.15.0-184.194~20.04.1, 5.15.0-184.194, 5.15.0-186.196~20.04.1, 5.15.0-186.196, 5.15.0-1075.79, 5.15.0-1095.103, 5.15.0-1104.109, 5.15.0-1108.114, 5.15.0-1111.120+fips1, 5.15.0-1112.122, 5.15.0-1112.122+fips1, 5.15.0.184.155, 5.15.0.186.166, 5.15.0.1075.78, 5.15.0.1095.94, 5.15.0.1104.100, 5.15.0.1108.107, 5.15.0.1111.115, 5.15.0.1112.102, 5.15.0.1112.109, 6.8.0-139.139+fips1, 6.8.0-1049.53, 6.8.0-1062.65~22.04.1, 6.8.0-1062.65+fips1, 6.8.0-1062.65.1, 6.8.0-1062.70, 6.8.0-1064.68, 6.8.0-1067.75, 6.8.0-1067.75+fips1, 6.8.1-1059.60~22.04.1, 6.8.1-1059.60
linux-aws (Ubuntu package) - addressed in versions 5.15.0-186.196+fips1, 5.15.0-1106.110, 5.15.0-1107.108, 5.15.0-1112.119~20.04.1, 5.15.0-1112.119, 5.15.0-1112.119+fips1, 5.15.0.186.109, 5.15.0.1106.103, 5.15.0.1107.107, 5.15.0.1112.108, 5.15.0.1112.115, 6.8.0-1064.67~22.04.1, 7.0.0-1009.9, 7.0.0-1015.15
linux-nvidia-tegra (Ubuntu package) - addressed in versions 5.15.0-1053.53, 5.15.0-1064.66, 5.15.0.1053.55, 5.15.0.1064.64, 6.8.0-1035.38
linux-nvidia-tegra-5.15 (Ubuntu package) - update to 5.15.0-1064.66~20.04.1
linux-intel-iot-realtime (Ubuntu package) - addressed in versions 5.15.0-1104.106, 5.15.0-1107.113~20.04.1, 5.15.0.1104.108
linux-raspi (Ubuntu package) - addressed in versions 5.15.0-1106.109, 5.15.0.1106.104
linux-intel-iotg (Ubuntu package) - addressed in versions 5.15.0-1107.113, 5.15.0.1107.106
linux-azure-5.15 (Ubuntu package) - addressed in versions 5.15.0-1109.115~20.04.1, 5.15.0-1117.126~20.04.1, 5.15.0-1117.126~20.04.2
linux-azure (Ubuntu package) - addressed in versions 5.15.0-1109.115, 5.15.0-1117.126, 5.15.0.1109.105, 5.15.0.1117.115, 6.8.0-1063.71~22.04.1, 6.8.0-1063.71, 7.0.0-1009.9, 7.0.0-1010.10
linux-gcp-5.15 (Ubuntu package) - update to 5.15.0-1112.122~20.04.1
linux-azure-fde (Ubuntu package) - addressed in versions 5.15.0-1117.126, 6.8.0-1062.69
linux-azure-fips (Ubuntu package) - addressed in versions 5.15.0-1117.126+fips1, 5.15.0.1117.102, 6.8.0-1063.71+fips2
linux-lowlatency (Ubuntu package) - addressed in versions 6.8.0-139.139.1~22.04.1, 6.8.0-139.139.1
linux-gcp-6.8 (Ubuntu package) - addressed in versions 6.8.0-1036.37, 6.8.0-1064.65, 6.8.0-1067.75~22.04.1
linux-oracle (Ubuntu package) - addressed in versions 6.8.0-1061.64~22.04.1, 6.8.0-1061.64
linux-azure-fde-6.8 (Ubuntu package) - update to 6.8.0-1062.69~22.04.1
linux-aws-fips (Ubuntu package) - update to 6.8.0-1064.67+fips1
linux-raspi-realtime (Ubuntu package) - update to 6.8.0-2053.55
linux-azure-fde-6.17 (Ubuntu package) - update to 6.17.0-1018.18~24.04.1
linux-azure-6.17 (Ubuntu package) - update to 6.17.0-1021.21~24.04.1
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16~24.04.1, 7.0.0-1016.16
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

External References

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