CVE-2026-90072 (GCVE-0-2026-90072)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:05 – Updated: 2026-09-17 16:05
VLAI
Title
net/sched: sfq: clamp quantum to avoid signed overflow soft lockup
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 86799499585af06a9431c9e7782658667bd62650 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 2017c355a5a1af77736cd1739fe922f69b5652dc (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 6581a82bf08ba5d4e2a6d4e3080df43315b296c4 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 9d782c662879c3adaaca30e05c36910ad11b9e54 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d72dbdfaeb5b9b8d884e0e036c3442754379ef74 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < aeb8196ecb95146e3410f635628e6cd47352b3e5 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < da16c31517cd2c06bb2c78c73e91ae192c01c426 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 816e90057ab1879562a5b7cc688e35bb9027ae97 (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.10.270 , ≤ 5.10.* (semver)
Unaffected: 5.15.221 , ≤ 5.15.* (semver)
Unaffected: 6.1.188 , ≤ 6.1.* (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.110 , ≤ 6.12.* (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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          "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."
        }
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    "datePublished": "2026-09-17T16:05:52.905Z",
    "dateReserved": "2026-09-11T19:38:34.784Z",
    "dateUpdated": "2026-09-17T16:05:52.905Z",
    "state": "PUBLISHED"
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            "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."
          }
        ],
        "id": "CVE-2026-90072",
        "lastModified": "2026-09-17T17:16:56.250",
        "metrics": {},
        "published": "2026-09-17T17:16:56.250",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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