GHSA-9GV9-CG8W-RC25

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-27 15:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops

fib_nlmsg_size() still estimates nexthop space as if every gateway is encoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an IPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA.

As a result, route notifications can allocate an skb that is too small. fib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the WARN_ON() that marks such failures as a fib_nlmsg_size() bug. With panic_on_warn set, this becomes a kernel panic.

Mirror the actual nexthop dump layout in fib_nlmsg_size(): account for IPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop layout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is actually present.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74657"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:39Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops\n\nfib_nlmsg_size() still estimates nexthop space as if every gateway is\nencoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an\nIPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA.\n\nAs a result, route notifications can allocate an skb that is too small.\nfib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the\nWARN_ON() that marks such failures as a fib_nlmsg_size() bug. With\npanic_on_warn set, this becomes a kernel panic.\n\nMirror the actual nexthop dump layout in fib_nlmsg_size(): account for\nIPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop\nlayout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is\nactually present.",
  "id": "GHSA-9gv9-cg8w-rc25",
  "modified": "2026-08-27T15:31:31Z",
  "published": "2026-08-22T18:30:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74657"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0f0ca602941d0a81ae9514943ca06c55159c6385"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4a5dfbae5179f6574695012a980476254df2d295"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4ff9548d84945d2cbf9e4c207288063a200ea397"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5307a53599fa762c06e475ee4a375252074fd324"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7f80ad373ce4a7af5367ff273cea0f16e91387f3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9b22f13524fa0de0d963bbd3002df6c28bae3395"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a59edda6eda1252340354322d8ab318b2e9052fb"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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