GHSA-WQ2R-F96J-67J9
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 12:31In the Linux kernel, the following vulnerability has been resolved:
net/sched: sfq: clamp quantum in change path
sfq_change() accepts any non-negative quantum (only rejects (int)ctl->quantum < 0). With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service).
Add max(256U, ...) matching fq_codel_change(). Reject quantum > 1<<20 with -EINVAL, matching fq_codel_change() and the init clamp.
Conditions to recreate the bug: CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices).
tc qdisc add dev dummy0 root sfq tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size_log 15 cell_log 0
{
"affected": [],
"aliases": [
"CVE-2026-98012"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:29Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sfq: clamp quantum in change path\n\nsfq_change() accepts any non-negative quantum (only rejects\n(int)ctl-\u003equantum \u003c 0). With a crafted size table qdisc_pkt_len reaches\n~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times\nunder the qdisc lock (a soft lockup / denial of service).\n\nAdd max(256U, ...) matching fq_codel_change(). Reject quantum \u003e 1\u003c\u003c20\nwith -EINVAL, matching fq_codel_change() and the init clamp.\n\nConditions to recreate the bug:\n CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via\n unshare -Urn suffices).\n\n tc qdisc add dev dummy0 root sfq\n tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size_log 15 cell_log 0",
"id": "GHSA-wq2r-f96j-67j9",
"modified": "2026-09-25T12:31:32Z",
"published": "2026-09-25T12:31:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98012"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/534cd7ecbbc6e8a974f4003a5c1557439c6e0a72"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e6c1cb728e389354203a72bc77464c222a247aeb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f3820dce042a673fcb28cc31c87ee14257e21a17"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fb9f88a33c516ea5c0bcd9a22ca288b246b34567"
}
],
"schema_version": "1.4.0",
"severity": []
}
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