GHSA-VP9R-6W4F-8WMQ

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31
VLAI
Details

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

tcp: fix TFO max_qlen accounting across reuseport migration

A listener's TCP_FASTOPEN max_qlen stops being accurate and lets through far more pending Fast Open requests than it was configured for.

This only shows up with SO_REUSEPORT listener migration, where closing a listener hands its still-pending TFO children over to a surviving one.

fastopenq.qlen is charged in tcp_fastopen_create_child() when the child is created and uncharged in reqsk_fastopen_remove() when the handshake completes. The uncharge follows rsk_listener of the request the child points at, and inet_reqsk_clone() has repointed the child at a new request owned by the new listener, so the ++ and the -- land on two different sockets. The new listener's qlen drifts negative and its limit no longer binds.

Charge the new listener during migration, like reqsk_queue_migrated() already does for queue->young and queue->qlen.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-74696"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:44Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix TFO max_qlen accounting across reuseport migration\n\nA listener\u0027s TCP_FASTOPEN max_qlen stops being accurate and lets through\nfar more pending Fast Open requests than it was configured for.\n\nThis only shows up with SO_REUSEPORT listener migration, where closing a\nlistener hands its still-pending TFO children over to a surviving one.\n\nfastopenq.qlen is charged in tcp_fastopen_create_child() when the child\nis created and uncharged in reqsk_fastopen_remove() when the handshake\ncompletes.  The uncharge follows rsk_listener of the request the child\npoints at, and inet_reqsk_clone() has repointed the child at a new\nrequest owned by the new listener, so the ++ and the -- land on two\ndifferent sockets.  The new listener\u0027s qlen drifts negative and its\nlimit no longer binds.\n\nCharge the new listener during migration, like reqsk_queue_migrated()\nalready does for queue-\u003eyoung and queue-\u003eqlen.",
  "id": "GHSA-vp9r-6w4f-8wmq",
  "modified": "2026-08-25T06:31:28Z",
  "published": "2026-08-22T18:30:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74696"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/585fc5247d14939a561056aa2addd9b7c2b1f670"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6e10ee56524a26b250229ad348637825646ddb88"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a0ab2ba83e35159d81cec830a92e885ecf8139be"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a66e869cf0c90c1e47ae75f72b6482acbfc808ff"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b6247e0f96bd825ffb2005257f6177b5e642dee6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d974618b2097453778389d385e3741629c40e0a3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e98f0d80b9cccb5f828425d2004f9686e7d1ae24"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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