---
id: CVE-2026-72421
title: 'ipv4: fib: Don''t ignore error route in local/main tables.'
summary: |-
  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 o…
severity: critical
cvss: 10
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    a29e95fbc51e8a1b932773fd0e259b2080881443
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    5ae18d87a45698e8244d0fcba64c658c35a7dd3d
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    9127589aabdee588278e8d0d0bd3709a760a92c8
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    49eaf1403201357762d745a35882fb734107d763
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    fd25996f57a95d56bc568c89b4921edcf334b7d8
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    828fad4fd418bcdb9f5d66fec0d184c52a85ec31
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    a668fa160247d7bbe921548cb845f607b8b9305f
  - >-
    Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 <
    b72f0db64205d9ce462038ba995d5d31eff32dc1
  - Linux 3.6
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T18:49:34.990573Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:23.102Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72421'
references:
  - url: 'https://git.kernel.org/stable/c/a29e95fbc51e8a1b932773fd0e259b2080881443'
  - url: 'https://git.kernel.org/stable/c/5ae18d87a45698e8244d0fcba64c658c35a7dd3d'
  - url: 'https://git.kernel.org/stable/c/9127589aabdee588278e8d0d0bd3709a760a92c8'
  - url: 'https://git.kernel.org/stable/c/49eaf1403201357762d745a35882fb734107d763'
  - url: 'https://git.kernel.org/stable/c/fd25996f57a95d56bc568c89b4921edcf334b7d8'
  - url: 'https://git.kernel.org/stable/c/828fad4fd418bcdb9f5d66fec0d184c52a85ec31'
  - url: 'https://git.kernel.org/stable/c/a668fa160247d7bbe921548cb845f607b8b9305f'
  - url: 'https://git.kernel.org/stable/c/b72f0db64205d9ce462038ba995d5d31eff32dc1'
tags:
  - cve.org
epss: 0.00595
epssPercentile: 0.47334
ingestedAt: '2026-10-16T19:46:24.396Z'
---

## Overview

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.

## Affected

- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < a29e95fbc51e8a1b932773fd0e259b2080881443`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < 5ae18d87a45698e8244d0fcba64c658c35a7dd3d`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < 9127589aabdee588278e8d0d0bd3709a760a92c8`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < 49eaf1403201357762d745a35882fb734107d763`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < fd25996f57a95d56bc568c89b4921edcf334b7d8`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < 828fad4fd418bcdb9f5d66fec0d184c52a85ec31`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < a668fa160247d7bbe921548cb845f607b8b9305f`
- `Linux >= f4530fa574df4d833506c53697ed1daa0d390bf4 < b72f0db64205d9ce462038ba995d5d31eff32dc1`
- `Linux 3.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.