GHSA-QG6M-CV4G-HX6Q

Vulnerability from github – Published: 2026-10-18 18:31 – Updated: 2026-10-18 18:31
VLAI
Details

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

net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure

flow_offload_alloc() returns NULL when the conntrack entry is dying (e.g. raced with a conntrack flush) or when the GFP_ATOMIC allocation fails; both are expected under load and neither is a kernel bug. This path runs from softirq on every committed packet, so with panic_on_warn=1 an unprivileged user can panic the box just by racing a conntrack flush against a tc ... action ct commit classifier.

Reproduced with a custom repro under QEMU: a small, fixed set of UDP flows through tc filter ... action ct commit on lo, raced against threads flooding bare ctnetlink CT_DELETE (flush) requests. Hits WARNING: net/sched/act_ct.c:437 (tcf_ct_flow_table_add(), inlined into tcf_ct_act() in this build) within ~15s on the unpatched kernel; same setup is clean on the patched kernel. The fix itself is behavior-preserving: both branches already did goto err_alloc before and after, only the WARN is removed.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98622"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:15Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: don\u0027t WARN on benign flow_offload_alloc() failure\n\nflow_offload_alloc() returns NULL when the conntrack entry is dying\n(e.g. raced with a conntrack flush) or when the GFP_ATOMIC allocation\nfails; both are expected under load and neither is a kernel bug. This\npath runs from softirq on every committed packet, so with\npanic_on_warn=1 an unprivileged user can panic the box just by racing\na conntrack flush against a `tc ... action ct commit` classifier.\n\nReproduced with a custom repro under QEMU: a small, fixed set of UDP\nflows through `tc filter ... action ct commit` on lo, raced against\nthreads flooding bare ctnetlink CT_DELETE (flush) requests. Hits\nWARNING: net/sched/act_ct.c:437 (tcf_ct_flow_table_add(), inlined\ninto tcf_ct_act() in this build) within ~15s on the unpatched kernel;\nsame setup is clean on the patched kernel. The fix itself is\nbehavior-preserving: both branches already did `goto err_alloc`\nbefore and after, only the WARN is removed.",
  "id": "GHSA-qg6m-cv4g-hx6q",
  "modified": "2026-10-18T18:31:57Z",
  "published": "2026-10-18T18:31:56Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98622"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/00734f3684fcec42c319bedfe68a5d357c720b53"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/424ba52c0058deeb940d02cba52eb0aeb288db33"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/47abe7a5c4eb53269aca3506446f851572a059a3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/650787233c2fd6e515a7c5f371019a9fa080ccd2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/af475f599270e59313552e6c6f3af8507da672b8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d512c484bd93a5f2794aa03c9faeb7bcb82dbd4a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d805560ad69cb266d669341ca01e26bffb0d2c67"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e8fcf3f08834e939b797311742ee72b1e2a08096"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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