Always-Incorrect Control Flow Implementation in Linux kernel - CVE-2026-72421

Vulnerability identifier: #VU143026

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-72421

CWE-ID: CWE-670

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to bypass intended unreachable routing behavior.

The vulnerability exists due to improper control flow in fib_lookup() in the IPv4 FIB lookup logic when performing route lookups with CONFIG_IP_MULTIPLE_TABLES enabled and no rule added. A local user can configure routes that trigger lookup of the merged local/main table followed by the default table to bypass intended unreachable routing behavior.

The issue occurs because an error route result from the local or main table can be overwritten by a subsequent lookup in the default table.

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
kgraft-patch-4_12_14-122_328-default
dlm-kmp-default
kernel-default-man
kernel-macros
kernel-devel
kernel-source
kernel-default-devel-debuginfo
kernel-default-base
kernel-default-devel
cluster-md-kmp-default
gfs2-kmp-default
ocfs2-kmp-default-debuginfo
gfs2-kmp-default-debuginfo
kernel-default
ocfs2-kmp-default
kernel-default-base-debuginfo
dlm-kmp-default-debuginfo
cluster-md-kmp-default-debuginfo
kernel-syms
kernel-default-kgraft
kernel-default-debuginfo
kernel-default-kgraft-devel
kernel-default-debugsource

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
dlm-kmp-default - update to 4.12.14-122.328.1
kernel-default-man - update to 4.12.14-122.328.1
kernel-macros - update to 4.12.14-122.328.1
kernel-devel - update to 4.12.14-122.328.1
kernel-source - update to 4.12.14-122.328.1
kernel-default-devel-debuginfo - update to 4.12.14-122.328.1
kernel-default-base - 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
kernel-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-debuginfo - 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

• https://git.kernel.org/stable/c/49eaf1403201357762d745a35882fb734107d763
• https://git.kernel.org/stable/c/5ae18d87a45698e8244d0fcba64c658c35a7dd3d
• https://git.kernel.org/stable/c/828fad4fd418bcdb9f5d66fec0d184c52a85ec31
• https://git.kernel.org/stable/c/9127589aabdee588278e8d0d0bd3709a760a92c8
• https://git.kernel.org/stable/c/a29e95fbc51e8a1b932773fd0e259b2080881443
• https://git.kernel.org/stable/c/a668fa160247d7bbe921548cb845f607b8b9305f
• https://git.kernel.org/stable/c/b72f0db64205d9ce462038ba995d5d31eff32dc1
• https://git.kernel.org/stable/c/fd25996f57a95d56bc568c89b4921edcf334b7d8

• Always-Incorrect Control Flow Implementation in Linux kernel net
• SUSE update for the Linux Kernel