CVE-2026-72421

ipv4: fib: Don't ignore error route in local/main tables.

State: Published
Severity: 10.0 Critical
Published: Aug 15, 2026
Updated: Oct 16, 2026
Reserved: Aug 9, 2026

Description

In the Linux kernel, the following vulnerability has been resolved:

ipv4: fib: Don't ignore error route in local/main tables.

When CONFIG_IP_MULTIPLE_TABLES is enabled but no rule is added, fib_lookup() performs route lookup directly on two tables.

Since the first lookup does not properly bail out, the result of an error route in the merged local/main table could be overwritten by another route in the default table:

# unshare -n # ip link set lo up # ip route add 192.168.0.0/24 dev lo table 253 # ip route add unreachable 192.168.0.0/24 # ip route get 192.168.0.1 192.168.0.1 dev lo table default uid 0 cache <local>

Once a random rule is added, the error route is respected:

# ip rule add table 0 # ip rule del table 0 # ip route get 192.168.0.1 RTNETLINK answers: No route to host

Let's fix the inconsistent behaviour.

Scores

CVSS	Score	Vector	Source
3.1	10.0 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	f4530fa574df4d833506c53697ed1daa0d390bf4 to before a29e95fbc51e8a1b932773fd0e259b2080881443Affected f4530fa574df4d833506c53697ed1daa0d390bf4 to before 5ae18d87a45698e8244d0fcba64c658c35a7dd3dAffected f4530fa574df4d833506c53697ed1daa0d390bf4 to before 9127589aabdee588278e8d0d0bd3709a760a92c8Affected f4530fa574df4d833506c53697ed1daa0d390bf4 to before 49eaf1403201357762d745a35882fb734107d763Affected f4530fa574df4d833506c53697ed1daa0d390bf4 to before fd25996f57a95d56bc568c89b4921edcf334b7d8Affected f4530fa574df4d833506c53697ed1daa0d390bf4 to before 828fad4fd418bcdb9f5d66fec0d184c52a85ec31Affected f4530fa574df4d833506c53697ed1daa0d390bf4 to before a668fa160247d7bbe921548cb845f607b8b9305fAffected f4530fa574df4d833506c53697ed1daa0d390bf4 to before b72f0db64205d9ce462038ba995d5d31eff32dc1Affected
LinuxLinux	3.6Affected before 3.6Not affected 5.10.261 through 5.10.Not affected 5.15.212 through 5.15.Not affected 6.1.178 through 6.1.Not affected 6.6.145 through 6.6.Not affected 6.12.97 through 6.12.Not affected 6.18.40 through 6.18.Not affected 7.1.5 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

f4530fa574df4d833506c53697ed1daa0d390bf4 to before a29e95fbc51e8a1b932773fd0e259b2080881443Affected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before 5ae18d87a45698e8244d0fcba64c658c35a7dd3dAffected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before 9127589aabdee588278e8d0d0bd3709a760a92c8Affected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before 49eaf1403201357762d745a35882fb734107d763Affected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before fd25996f57a95d56bc568c89b4921edcf334b7d8Affected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before 828fad4fd418bcdb9f5d66fec0d184c52a85ec31Affected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before a668fa160247d7bbe921548cb845f607b8b9305fAffected
f4530fa574df4d833506c53697ed1daa0d390bf4 to before b72f0db64205d9ce462038ba995d5d31eff32dc1Affected

LinuxLinux

3.6Affected
before 3.6Not affected
5.10.261 through 5.10.*Not affected
5.15.212 through 5.15.*Not affected
6.1.178 through 6.1.*Not affected
6.6.145 through 6.6.*Not affected
6.12.97 through 6.12.*Not affected
6.18.40 through 6.18.*Not affected
7.1.5 through 7.1.*Not affected
7.2 and laterNot affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.