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.

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

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