{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-72421 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-72421 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-72421 and fix it if it is affected.\n\nWhat it is: CVE-2026-72421 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-72421 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-72421/ (Markdown: https://insights.sbomify.com/CVE-2026-72421/index.md)","id":"CVE-2026-72421","markdown":"https://insights.sbomify.com/CVE-2026-72421/index.md","name":"CVE-2026-72421","record":{"aliases":["BELL-CVE-2026-72421","DEBIAN-CVE-2026-72421","GHSA-66j4-c66h-jm7x","UBUNTU-CVE-2026-72421"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["security_bypass"],"network_reachable":"yes","non_default_config":true,"product_category":"Linux kernel networking","requires_auth":"none","summary":"A logic error in Linux kernel IPv4 routing allows bypassing unreachable route restrictions when multiple tables are enabled but no rules are configured.","user_interaction":"not_required","vuln_class":"misconfiguration"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":10,"severity":"critical","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","version":"3.1"},"cwes":[],"description":"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.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"ipv4: fib: Don't ignore error route in local/main tables.","id":"CVE-2026-72421","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"misconfiguration","year":"2026"},"n_packages":0,"n_references":8,"next":{"headline":"ksmbd: fix use-after-free of conn-\u003epreauth_info in concurrent SMB2 NEGOTIATE","id":"CVE-2026-72422"},"packages":[],"prev":{"headline":"md/raid5: avoid R5_Overlap races while breaking stripe batches","id":"CVE-2026-72420"},"products":["Linux"],"published":"2026-08-15","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-10-16","vendors":["Linux"]},"summary":"A logic error in Linux kernel IPv4 routing allows bypassing unreachable route restrictions when multiple tables are enabled but no rules are configured.","url":"https://insights.sbomify.com/CVE-2026-72421/"}