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CVE-2026-72421 (GCVE-0-2026-72421)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:44
VLAI
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 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.
Severity
10 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < a29e95fbc51e8a1b932773fd0e259b2080881443 (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < 5ae18d87a45698e8244d0fcba64c658c35a7dd3d (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < 9127589aabdee588278e8d0d0bd3709a760a92c8 (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < 49eaf1403201357762d745a35882fb734107d763 (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < fd25996f57a95d56bc568c89b4921edcf334b7d8 (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < 828fad4fd418bcdb9f5d66fec0d184c52a85ec31 (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < a668fa160247d7bbe921548cb845f607b8b9305f (git)
Affected: f4530fa574df4d833506c53697ed1daa0d390bf4 , < b72f0db64205d9ce462038ba995d5d31eff32dc1 (git)
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Linux Linux Affected: 3.6
Unaffected: 0 , < 3.6 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: fib: Don\u0027t 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\u0027s fix the inconsistent behaviour."
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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-19T17:54:15+00:00",
      "cve": "CVE-2026-72421",
      "id": "CVE-2026-72421",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ipv4: fib: Don\u0027t ignore error route in local/main tables",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72421.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.