{
  "affected": [
    {
      "ranges": [
        {
          "events": [
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              "introduced": "fc07a232326a623d0be482e307c08ea7049c2846"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
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              "introduced": "3bed2abab4a682d426624ce9add9d7b6d475d4e4"
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    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
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          ],
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        },
        {
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          ],
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        },
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          "type": "ECOSYSTEM"
        },
        {
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            }
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          "type": "ECOSYSTEM"
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  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99074.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: stop PMTU walk when nexthop group shrinks\n\nCommit 7d3f3b4367f3 (\"net: ipv4: Cache pmtu for all packet paths if\nmultipath enabled\") made __ip_rt_update_pmtu() update every path.\n\nFor nexthop objects, fib_info_num_path() and fib_info_nhc()\nindependently load nh-\u003enh_grp.  RCU protects each group's lifetime but\ndoes not make the loads observe the same group.  If replacement shrinks\nthe group after the loop accepts an index, fib_info_nhc() returns NULL\nand update_or_create_fnhe() dereferences it.\n\nA deterministic probe only widened the existing window between the real\noperations.  On v7.2, an RTM_NEWNEXTHOP replacement published a\none-member group after the PMTU reader accepted index 1 from a two-member\ngroup, producing:\n\n  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n  RIP: update_or_create_fnhe+0x45/0x15b0\n\nStop when the indexed path is absent.  Groups are dense, so no later\nindex exists in that snapshot.  The same real-writer window completed\n114,423 PMTU iterations without an oops with this check.  A reproducer\nis available on request.\n\nReplacement requires CAP_NET_ADMIN in the network namespace.  Where\nunprivileged user namespaces are permitted, a local user can obtain it\nin a new user and network namespace.",
  "id": "CVE-2026-99074",
  "modified": "2026-11-01T02:30:25.357746635Z",
  "published": "2026-10-23T12:23:17.866Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99074.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99074"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.2",
  "summary": "ipv4: stop PMTU walk when nexthop group shrinks"
}