CVE-2026-90072 (GCVE-0-2026-90072)
Vulnerability from cvelistv5
Published
2026-09-17 16:05
Modified
2026-10-19 08:57
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: sfq: clamp quantum to avoid signed overflow soft lockup sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN and INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning sfq_dequeue() under the qdisc lock. Clamp the quantum to [256, 1 << 20] so the refill loop terminates. The lower bound also covers q->quantum == 0 (psched_mtu() returning 0), which spins sfq_dequeue() identically. sfq_change() already rejects a negative quantum, so only the init path was exposed. Conditions to recreate the bug: a device whose MTU (plus hard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_sfq.c"
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              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sfq: clamp quantum to avoid signed overflow soft lockup\n\nsfq_init() sets q-\u003equantum = psched_mtu(qdisc_dev(sch)) (unsigned). A\ndevice with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU\n2147483634) makes psched_mtu() return 0x80000000, so slot-\u003eallot = INT_MIN\nand INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning\nsfq_dequeue() under the qdisc lock.\n\nClamp the quantum to [256, 1 \u003c\u003c 20] so the refill loop terminates. The\nlower bound also covers q-\u003equantum == 0 (psched_mtu() returning 0),\nwhich spins sfq_dequeue() identically. sfq_change() already rejects a\nnegative quantum, so only the init path was exposed.\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) wraps psched_mtu() into the sign bit (e.g. a dummy\ndevice with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:57:29.264Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/86799499585af06a9431c9e7782658667bd62650"
        },
        {
          "url": "https://git.kernel.org/stable/c/2017c355a5a1af77736cd1739fe922f69b5652dc"
        },
        {
          "url": "https://git.kernel.org/stable/c/6581a82bf08ba5d4e2a6d4e3080df43315b296c4"
        },
        {
          "url": "https://git.kernel.org/stable/c/9d782c662879c3adaaca30e05c36910ad11b9e54"
        },
        {
          "url": "https://git.kernel.org/stable/c/d72dbdfaeb5b9b8d884e0e036c3442754379ef74"
        },
        {
          "url": "https://git.kernel.org/stable/c/aeb8196ecb95146e3410f635628e6cd47352b3e5"
        },
        {
          "url": "https://git.kernel.org/stable/c/da16c31517cd2c06bb2c78c73e91ae192c01c426"
        },
        {
          "url": "https://git.kernel.org/stable/c/816e90057ab1879562a5b7cc688e35bb9027ae97"
        }
      ],
      "title": "net/sched: sfq: clamp quantum to avoid signed overflow soft lockup",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90072",
    "datePublished": "2026-09-17T16:05:52.905Z",
    "dateReserved": "2026-09-11T19:38:34.784Z",
    "dateUpdated": "2026-10-19T08:57:29.264Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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