GHSA-97JQ-2G8V-56HQ
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: fq: clamp quantum and initial_quantum in change path
The fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and TCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to [1, 1<<20]. A user can override the init clamp via tc qdisc change, restoring the small-quantum deficit spin that the init clamp prevents.
Narrow iq_range.max to 1<<20 so TCA_FQ_INITIAL_QUANTUM is rejected at parse time. Clamp TCA_FQ_QUANTUM to [256, 1<<20] in fq_change() and fq_init() quantum to [256, 1<<20] for tiny-MTU devices.
Conditions to recreate the bug: CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices).
tc qdisc add dev dummy0 root fq tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0
{
"affected": [],
"aliases": [
"CVE-2026-90050"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:16:53Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fq: clamp quantum and initial_quantum in change path\n\nThe fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and\nTCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to\n[1, 1\u003c\u003c20]. A user can override the init clamp via tc qdisc change,\nrestoring the small-quantum deficit spin that the init clamp prevents.\n\nNarrow iq_range.max to 1\u003c\u003c20 so TCA_FQ_INITIAL_QUANTUM is rejected at\nparse time. Clamp TCA_FQ_QUANTUM to [256, 1\u003c\u003c20] in fq_change() and\nfq_init() quantum to [256, 1\u003c\u003c20] for tiny-MTU devices.\n\nConditions to recreate the bug:\n CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via\n unshare -Urn suffices).\n\n tc qdisc add dev dummy0 root fq\n tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0",
"id": "GHSA-97jq-2g8v-56hq",
"modified": "2026-09-17T18:31:48Z",
"published": "2026-09-17T18:31:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90050"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/72e9387884554f47b03bfd40fb8b2bf52789c68d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175"
}
],
"schema_version": "1.4.0",
"severity": []
}
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