{"id":"CVE-2026-90050","published":"2026-09-17T17:16:53.363","lastModified":"2026-09-17T17:16:53.363","description":"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<<20]. 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<<20 so TCA_FQ_INITIAL_QUANTUM is rejected at\nparse time. Clamp TCA_FQ_QUANTUM to [256, 1<<20] in fq_change() and\nfq_init() quantum to [256, 1<<20] 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","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622","tags":[]},{"url":"https://git.kernel.org/stable/c/72e9387884554f47b03bfd40fb8b2bf52789c68d","tags":[]},{"url":"https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f","tags":[]},{"url":"https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}