GHSA-783H-5CFX-MM7X
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-90072"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:16:56Z",
"severity": null
},
"details": "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": "GHSA-783h-5cfx-mm7x",
"modified": "2026-09-17T18:31:49Z",
"published": "2026-09-17T18:31:49Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90072"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2017c355a5a1af77736cd1739fe922f69b5652dc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6581a82bf08ba5d4e2a6d4e3080df43315b296c4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/816e90057ab1879562a5b7cc688e35bb9027ae97"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/86799499585af06a9431c9e7782658667bd62650"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9d782c662879c3adaaca30e05c36910ad11b9e54"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/aeb8196ecb95146e3410f635628e6cd47352b3e5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d72dbdfaeb5b9b8d884e0e036c3442754379ef74"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/da16c31517cd2c06bb2c78c73e91ae192c01c426"
}
],
"schema_version": "1.4.0",
"severity": []
}
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