CVE-2026-98622 (GCVE-0-2026-98622)
Vulnerability from cvelistv5
Published
2026-10-18 15:19
Modified
2026-10-19 09:22
Severity ?
Summary
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
Version: 64ff70b80fd403110b67dd9f7184a604fdb0da43
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{
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:22:50.359Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e8fcf3f08834e939b797311742ee72b1e2a08096"
        },
        {
          "url": "https://git.kernel.org/stable/c/af475f599270e59313552e6c6f3af8507da672b8"
        },
        {
          "url": "https://git.kernel.org/stable/c/424ba52c0058deeb940d02cba52eb0aeb288db33"
        },
        {
          "url": "https://git.kernel.org/stable/c/d512c484bd93a5f2794aa03c9faeb7bcb82dbd4a"
        },
        {
          "url": "https://git.kernel.org/stable/c/d805560ad69cb266d669341ca01e26bffb0d2c67"
        },
        {
          "url": "https://git.kernel.org/stable/c/00734f3684fcec42c319bedfe68a5d357c720b53"
        },
        {
          "url": "https://git.kernel.org/stable/c/650787233c2fd6e515a7c5f371019a9fa080ccd2"
        },
        {
          "url": "https://git.kernel.org/stable/c/47abe7a5c4eb53269aca3506446f851572a059a3"
        }
      ],
      "title": "net/sched: act_ct: don\u0027t WARN on benign flow_offload_alloc() failure",
      "x_generator": {
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98622",
    "datePublished": "2026-10-18T15:19:42.514Z",
    "dateReserved": "2026-09-25T10:25:14.360Z",
    "dateUpdated": "2026-10-19T09:22:50.359Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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