NULL pointer dereference in Linux kernel - CVE-2026-53403

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Main Vulnerability Database Vulnerabilities #VU138863

NULL pointer dereference in Linux kernel - CVE-2026-53403

Published: July 21, 2026


Vulnerability identifier: #VU138863
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-53403
CWE-ID: CWE-476
Exploitation vector: Local access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a null pointer dereference in fb_videomode_to_var in the fbdev subsystem when processing a userspace-supplied modelist that does not contain the current framebuffer mode. A local user can supply a crafted mode list to trigger a kernel crash and cause a denial of service.

Exploitation requires fbcon to be unbound so that the current mode is left without a matching entry before a later console takeover occurs.


Affected software

Linux kernel
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Live Patching
Ubuntu
kgraft-patch-4_12_14-122_328-default
kernel-default-debuginfo
kernel-default-devel
cluster-md-kmp-default
gfs2-kmp-default
ocfs2-kmp-default-debuginfo
gfs2-kmp-default-debuginfo
dlm-kmp-default
ocfs2-kmp-default
kernel-default-base-debuginfo
dlm-kmp-default-debuginfo
cluster-md-kmp-default-debuginfo
kernel-syms
kernel-default-kgraft
kernel-default-kgraft-devel
kernel-default-debugsource
kernel-default
kernel-default-base
kernel-default-devel-debuginfo
kernel-source
kernel-devel
kernel-macros
kernel-default-man
linux (Ubuntu package)
linux-azure (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)

How to mitigate CVE-2026-53403

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kgraft-patch-4_12_14-122_328-default - update to 1-8.5.1
kernel-default-debuginfo - update to 4.12.14-122.328.1
kernel-default-devel - update to 4.12.14-122.328.1
cluster-md-kmp-default - update to 4.12.14-122.328.1
gfs2-kmp-default - update to 4.12.14-122.328.1
ocfs2-kmp-default-debuginfo - update to 4.12.14-122.328.1
gfs2-kmp-default-debuginfo - update to 4.12.14-122.328.1
dlm-kmp-default - update to 4.12.14-122.328.1
ocfs2-kmp-default - update to 4.12.14-122.328.1
kernel-default-base-debuginfo - update to 4.12.14-122.328.1
dlm-kmp-default-debuginfo - update to 4.12.14-122.328.1
cluster-md-kmp-default-debuginfo - update to 4.12.14-122.328.1
kernel-syms - update to 4.12.14-122.328.1
kernel-default-kgraft - update to 4.12.14-122.328.1
kernel-default-kgraft-devel - update to 4.12.14-122.328.1
kernel-default-debugsource - update to 4.12.14-122.328.1
kernel-default - update to 4.12.14-122.328.1
kernel-default-base - update to 4.12.14-122.328.1
kernel-default-devel-debuginfo - update to 4.12.14-122.328.1
kernel-source - update to 4.12.14-122.328.1
kernel-devel - update to 4.12.14-122.328.1
kernel-macros - update to 4.12.14-122.328.1
kernel-default-man - update to 4.12.14-122.328.1
linux (Ubuntu package) - addressed in versions 7.0.0-31.31, 7.0.0-31.31.1, 7.0.0-31.31~24.04.1, 7.0.0-1006.7, 7.0.0-1011.11~24.04.1, 7.0.0-1012.12, 7.0.0-1012.12~24.04.1
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1011.11, 7.0.0-1014.14
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1

External References

Related Security Bulletins