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

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Main Vulnerability Database Vulnerabilities #VU143026

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

Published: August 15, 2026


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

Vulnerability details

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.


Affected software

Linux kernel
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Desktop 15
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 Workstation Extension 15
SUSE Linux Enterprise Live Patching
SUSE Real Time Module
Basesystem Module
Public Cloud Module
Legacy Module
Development Tools Module
Ubuntu
linux (Ubuntu package)
linux-kvm (Ubuntu package)
linux-gcp (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-raspi (Ubuntu package)
linux-oracle (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-gke (Ubuntu package)
linux-aws-5.15 (Ubuntu package)
linux-lowlatency-hwe-5.15 (Ubuntu package)
linux-hwe-5.15 (Ubuntu package)
linux-fips (Ubuntu package)
linux-azure-5.15 (Ubuntu package)
linux-ibm-5.15 (Ubuntu package)
linux-gkeop (Ubuntu package)
linux-intel-iotg (Ubuntu package)
linux-azure-fde-5.15 (Ubuntu package)
linux-nvidia-tegra (Ubuntu package)
linux-nvidia-tegra-igx (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-realtime (Ubuntu package)
linux-ibm (Ubuntu package)
linux-intel-iotg-5.15 (Ubuntu package)
linux-oracle-5.15 (Ubuntu package)
linux-gcp-5.15 (Ubuntu package)
linux-nvidia-tegra-5.15 (Ubuntu package)
linux-azure-fde (Ubuntu package)
linux-xilinx-zynqmp (Ubuntu package)
linux-intel-iot-realtime (Ubuntu package)
linux-gcp-fips (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-azure-fips (Ubuntu package)
linux-hwe-6.8 (Ubuntu package)
linux-lowlatency-hwe-6.8 (Ubuntu package)
linux-azure-fde-6.8 (Ubuntu package)
linux-aws-6.8 (Ubuntu package)
linux-azure-6.8 (Ubuntu package)
linux-oracle-6.8 (Ubuntu package)
linux-nvidia-lowlatency (Ubuntu package)
linux-ibm-6.8 (Ubuntu package)
linux-gcp-6.8 (Ubuntu package)
linux-raspi-realtime (Ubuntu package)
linux-realtime-6.8 (Ubuntu package)
linux-nvidia-bos (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-aws-7.0 (Ubuntu package)
linux-nvidia-7.0 (Ubuntu package)
kgraft-patch-4_12_14-122_328-default
kernel-livepatch-6_4_0-150700_7_78-rt-debuginfo
kernel-livepatch-6_4_0-150700_7_78-rt
kernel-livepatch-SLE15-SP7-RT_Update_21-debugsource
kernel-livepatch-6_4_0-150700_53_84-default-debuginfo
kernel-livepatch-SLE15-SP7_Update_22-debugsource
kernel-livepatch-6_4_0-150700_53_84-default
kernel-default-man
kernel-default
kernel-macros
kernel-devel
kernel-source
kernel-default-devel-debuginfo
kernel-default-base
kernel-default-devel
gfs2-kmp-default
kernel-default-debugsource
kernel-default-kgraft-devel
kernel-default-debuginfo
kernel-default-kgraft
kernel-syms
cluster-md-kmp-default-debuginfo
dlm-kmp-default-debuginfo
cluster-md-kmp-default
ocfs2-kmp-default-debuginfo
gfs2-kmp-default-debuginfo
dlm-kmp-default
ocfs2-kmp-default
kernel-default-base-debuginfo
kernel-rt-devel
ocfs2-kmp-rt-debuginfo
cluster-md-kmp-rt-debuginfo
kernel-rt-debuginfo
kernel-rt-devel-debuginfo
kernel-rt
dlm-kmp-rt
kernel-syms-rt
kernel-rt-debugsource
cluster-md-kmp-rt
dlm-kmp-rt-debuginfo
gfs2-kmp-rt
gfs2-kmp-rt-debuginfo
ocfs2-kmp-rt
kernel-source-rt
kernel-devel-rt
kernel-azure-devel-debuginfo
reiserfs-kmp-default-debuginfo
kernel-default-livepatch-devel
kernel-default-livepatch
kernel-azure
kernel-azure-debugsource
kernel-azure-devel
kernel-azure-debuginfo
kernel-default-extra
kernel-default-extra-debuginfo
kernel-zfcpdump-debuginfo
reiserfs-kmp-default
kernel-zfcpdump
kernel-zfcpdump-debugsource
kernel-64kb
kernel-64kb-debuginfo
kernel-64kb-devel-debuginfo
kernel-64kb-debugsource
kernel-64kb-devel
kernel-docs
kernel-obs-build
kernel-obs-build-debugsource
linux-azure-7.0 (Ubuntu package)

How to mitigate CVE-2026-72421

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - addressed in versions 5.15.0-198.208, 6.8.0-147.147, 7.0.0-38.38
linux-kvm (Ubuntu package) - update to 5.15.0-1109.114
linux-gcp (Ubuntu package) - addressed in versions 5.15.0-1118.128, 6.8.0-1071.79, 7.0.0-1014.14
linux-aws (Ubuntu package) - addressed in versions 5.15.0-1117.124, 6.8.0-1067.70, 7.0.0-1014.14
linux-azure (Ubuntu package) - addressed in versions 5.15.0-1123.132, 6.8.0-1071.79, 7.0.0-1016.16, 7.0.0-1017.17
linux-raspi (Ubuntu package) - addressed in versions 5.15.0-1113.116, 6.8.0-1068.72, 7.0.0-1023.23
linux-oracle (Ubuntu package) - addressed in versions 5.15.0-1114.120, 6.8.0-1064.67, 7.0.0-1013.13
linux-lowlatency (Ubuntu package) - addressed in versions 5.15.0-195.205, 6.8.0-147.147.1
linux-gke (Ubuntu package) - addressed in versions 5.15.0-1113.119, 6.8.0-1066.74, 7.0.0-1008.9
linux-aws-5.15 (Ubuntu package) - update to 5.15.0-1117.124~20.04.1
linux-lowlatency-hwe-5.15 (Ubuntu package) - update to 5.15.0-195.205~20.04.1
linux-hwe-5.15 (Ubuntu package) - update to 5.15.0-198.208~20.04.1
linux-fips (Ubuntu package) - addressed in versions 5.15.0-198.208+fips1, 6.8.0-147.147+fips1
linux-azure-5.15 (Ubuntu package) - update to 5.15.0-1123.132~20.04.1
linux-ibm-5.15 (Ubuntu package) - update to 5.15.0-1111.115~20.04.1
linux-gkeop (Ubuntu package) - addressed in versions 5.15.0-1100.108, 6.8.0-1052.56
linux-intel-iotg (Ubuntu package) - update to 5.15.0-1112.118
linux-azure-fde-5.15 (Ubuntu package) - update to 5.15.0-1122.131~20.04.1
linux-nvidia-tegra (Ubuntu package) - addressed in versions 5.15.0-1070.72, 6.8.0-1035.38
linux-nvidia-tegra-igx (Ubuntu package) - update to 5.15.0-1059.59
linux-nvidia (Ubuntu package) - addressed in versions 5.15.0-1112.113, 6.8.0-1067.70, 7.0.0-1025.26
linux-realtime (Ubuntu package) - addressed in versions 5.15.0-1116.125, 6.8.1-1062.63, 7.0.0-38.38.1
linux-ibm (Ubuntu package) - addressed in versions 5.15.0-1111.115, 6.8.0-1067.68, 7.0.0-1015.15
linux-intel-iotg-5.15 (Ubuntu package) - update to 5.15.0-1112.118~20.04.1
linux-oracle-5.15 (Ubuntu package) - update to 5.15.0-1114.120~20.04.1
linux-gcp-5.15 (Ubuntu package) - update to 5.15.0-1118.128~20.04.1
linux-nvidia-tegra-5.15 (Ubuntu package) - update to 5.15.0-1070.72~20.04.1
linux-azure-fde (Ubuntu package) - addressed in versions 5.15.0-1122.131, 6.8.0-1069.76
linux-xilinx-zynqmp (Ubuntu package) - update to 5.15.0-1080.84
linux-intel-iot-realtime (Ubuntu package) - update to 5.15.0-1109.111
linux-gcp-fips (Ubuntu package) - addressed in versions 5.15.0-1118.128+fips1, 6.8.0-1071.79+fips1
linux-aws-fips (Ubuntu package) - addressed in versions 5.15.0-1117.124+fips1, 6.8.0-1067.70+fips1
linux-azure-fips (Ubuntu package) - addressed in versions 5.15.0-1123.132+fips1, 6.8.0-1071.79+fips1
linux-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149~22.04.1
linux-lowlatency-hwe-6.8 (Ubuntu package) - update to 6.8.0-149.149.1~22.04.1
linux-azure-fde-6.8 (Ubuntu package) - update to 6.8.0-1071.78~22.04.1
linux-aws-6.8 (Ubuntu package) - update to 6.8.0-1069.74~22.04.1
linux-azure-6.8 (Ubuntu package) - update to 6.8.0-1073.82~22.04.1
linux-oracle-6.8 (Ubuntu package) - update to 6.8.0-1067.71~22.04.1
linux-nvidia-lowlatency (Ubuntu package) - update to 6.8.0-1067.70.1
linux-ibm-6.8 (Ubuntu package) - update to 6.8.0-1069.70~22.04.1
linux-gcp-6.8 (Ubuntu package) - update to 6.8.0-1073.81~22.04.1
linux-raspi-realtime (Ubuntu package) - update to 6.8.0-2056.58
linux-realtime-6.8 (Ubuntu package) - update to 6.8.1-1064.65~22.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2022.23
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-38.38~24.04.4
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1013.13~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1015.15
linux-aws-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-nvidia-7.0 (Ubuntu package) - update to 7.0.0-1024.25~24.04.1
kgraft-patch-4_12_14-122_328-default - update to 1-8.5.1
kernel-livepatch-6_4_0-150700_7_78-rt-debuginfo - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_7_78-rt - update to 1-150700.1.3.1
kernel-livepatch-SLE15-SP7-RT_Update_21-debugsource - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_53_84-default-debuginfo - update to 1-150700.15.3.1
kernel-livepatch-SLE15-SP7_Update_22-debugsource - update to 1-150700.15.3.1
kernel-livepatch-6_4_0-150700_53_84-default - update to 1-150700.15.3.1
kernel-default-man - update to 4.12.14-122.328.1
kernel-default - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-macros - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-devel - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-source - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-devel-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-base - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1.150700.17.47.1
kernel-default-devel - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
gfs2-kmp-default - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-debugsource - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-kgraft-devel - update to 4.12.14-122.328.1
kernel-default-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-kgraft - update to 4.12.14-122.328.1
kernel-syms - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
cluster-md-kmp-default-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
dlm-kmp-default-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
cluster-md-kmp-default - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
ocfs2-kmp-default-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
gfs2-kmp-default-debuginfo - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
dlm-kmp-default - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
ocfs2-kmp-default - addressed in versions 4.12.14-122.328.1, 6.4.0-150700.53.84.1
kernel-default-base-debuginfo - update to 4.12.14-122.328.1
kernel-rt-devel - update to 6.4.0-150700.7.78.1
ocfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.78.1
cluster-md-kmp-rt-debuginfo - update to 6.4.0-150700.7.78.1
kernel-rt-debuginfo - update to 6.4.0-150700.7.78.1
kernel-rt-devel-debuginfo - update to 6.4.0-150700.7.78.1
kernel-rt - update to 6.4.0-150700.7.78.1
dlm-kmp-rt - update to 6.4.0-150700.7.78.1
kernel-syms-rt - update to 6.4.0-150700.7.78.1
kernel-rt-debugsource - update to 6.4.0-150700.7.78.1
cluster-md-kmp-rt - update to 6.4.0-150700.7.78.1
dlm-kmp-rt-debuginfo - update to 6.4.0-150700.7.78.1
gfs2-kmp-rt - update to 6.4.0-150700.7.78.1
gfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.78.1
ocfs2-kmp-rt - update to 6.4.0-150700.7.78.1
kernel-source-rt - update to 6.4.0-150700.7.78.1
kernel-devel-rt - update to 6.4.0-150700.7.78.1
kernel-azure-devel-debuginfo - update to 6.4.0-150700.53.84.1
reiserfs-kmp-default-debuginfo - update to 6.4.0-150700.53.84.1
kernel-default-livepatch-devel - update to 6.4.0-150700.53.84.1
kernel-default-livepatch - update to 6.4.0-150700.53.84.1
kernel-azure - update to 6.4.0-150700.53.84.1
kernel-azure-debugsource - update to 6.4.0-150700.53.84.1
kernel-azure-devel - update to 6.4.0-150700.53.84.1
kernel-azure-debuginfo - update to 6.4.0-150700.53.84.1
kernel-default-extra - update to 6.4.0-150700.53.84.1
kernel-default-extra-debuginfo - update to 6.4.0-150700.53.84.1
kernel-zfcpdump-debuginfo - update to 6.4.0-150700.53.84.1
reiserfs-kmp-default - update to 6.4.0-150700.53.84.1
kernel-zfcpdump - update to 6.4.0-150700.53.84.1
kernel-zfcpdump-debugsource - update to 6.4.0-150700.53.84.1
kernel-64kb - update to 6.4.0-150700.53.84.1
kernel-64kb-debuginfo - update to 6.4.0-150700.53.84.1
kernel-64kb-devel-debuginfo - update to 6.4.0-150700.53.84.1
kernel-64kb-debugsource - update to 6.4.0-150700.53.84.1
kernel-64kb-devel - update to 6.4.0-150700.53.84.1
kernel-docs - update to 6.4.0-150700.53.84.1
kernel-obs-build - update to 6.4.0-150700.53.84.1
kernel-obs-build-debugsource - update to 6.4.0-150700.53.84.1
linux-azure-7.0 (Ubuntu package) - addressed in versions 7.0.0-1016.16~24.04.1, 7.0.0-1017.17~24.04.1

External References

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