UNKNOWN NVD
CVE-2026-90050
In 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
In 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
References
- https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622
- https://git.kernel.org/stable/c/72e9387884554f47b03bfd40fb8b2bf52789c68d
- https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f
- https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175
This unknown severity vulnerability was published on 2026-09-17 via NVD.
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