{"id":"CVE-2026-72421","summary":"ipv4: fib: Don't ignore error route in local/main tables.","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: fib: Don't ignore error route in local/main tables.\n\nWhen CONFIG_IP_MULTIPLE_TABLES is enabled but no rule is added,\nfib_lookup() performs route lookup directly on two tables.\n\nSince the first lookup does not properly bail out, the result\nof an error route in the merged local/main table could be\noverwritten by another route in the default table:\n\n  # unshare -n\n  # ip link set lo up\n  # ip route add 192.168.0.0/24 dev lo table 253\n  # ip route add unreachable 192.168.0.0/24\n  # ip route get 192.168.0.1\n  192.168.0.1 dev lo table default uid 0\n      cache \u003clocal\u003e\n\nOnce a random rule is added, the error route is respected:\n\n  # ip rule add table 0\n  # ip rule del table 0\n  # ip route get 192.168.0.1\n  RTNETLINK answers: No route to host\n\nLet's fix the inconsistent behaviour.","modified":"2026-08-18T03:56:43.138714121Z","published":"2026-08-15T05:56:40.466Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72421.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/49eaf1403201357762d745a35882fb734107d763"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5ae18d87a45698e8244d0fcba64c658c35a7dd3d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/828fad4fd418bcdb9f5d66fec0d184c52a85ec31"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9127589aabdee588278e8d0d0bd3709a760a92c8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a29e95fbc51e8a1b932773fd0e259b2080881443"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a668fa160247d7bbe921548cb845f607b8b9305f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b72f0db64205d9ce462038ba995d5d31eff32dc1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fd25996f57a95d56bc568c89b4921edcf334b7d8"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72421.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72421"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"f4530fa574df4d833506c53697ed1daa0d390bf4"},{"fixed":"a29e95fbc51e8a1b932773fd0e259b2080881443"},{"fixed":"5ae18d87a45698e8244d0fcba64c658c35a7dd3d"},{"fixed":"9127589aabdee588278e8d0d0bd3709a760a92c8"},{"fixed":"49eaf1403201357762d745a35882fb734107d763"},{"fixed":"fd25996f57a95d56bc568c89b4921edcf334b7d8"},{"fixed":"828fad4fd418bcdb9f5d66fec0d184c52a85ec31"},{"fixed":"a668fa160247d7bbe921548cb845f607b8b9305f"},{"fixed":"b72f0db64205d9ce462038ba995d5d31eff32dc1"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72421.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.6.0"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72421.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N"}]}