CVE-2026-90074 net/sched: fq_pie: clamp default quantum to avoid signed overflow

Q: Is CVE-2026-90074 being exploited?

There is no known exploitation of CVE-2026-90074 in the wild and no public exploit code.

Not scored Published 17 Sep 2026 Updated 19 Oct 2026

A signed integer overflow in the Linux kernel's fq_pie scheduler can cause a soft lockup and denial of service when configured with a huge MTU.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-90074?

CVE-2026-90074 is a vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: fq_pie: clamp default quantum to avoid signed overflow

fq_pie_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) without clamping. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000, which overflows the signed flow->deficit to INT_MIN in fq_pie_qdisc_dequeue(), causing an infinite loop and soft lockup. Emulate fq_pie_policy which is already bounded to [1, 1 << 20]; clamp the default to [256, 1 << 20]. 256 matches fq_codel's floor and is a sane minimum for a DRR quantum.

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.

Which versions are affected by CVE-2026-90074?

How do I fix CVE-2026-90074?

Apply the vendor's patch.

Is CVE-2026-90074 being exploited?