CVE-2026-90075

CVE CVE-2026-90075EUVD EUVD-2026-81936Published 2026-09-17T16:05:54.000Z

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: net/sched: fq_codel: clamp default quantum and mtu fq_codel_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_codel_dequeue(), causing an infinite loop and soft lockup. Emulate fq_codel_change() and constrain to [256, FQ_CODEL_QUANTUM_MAX]. The same unclamped psched_mtu() is assigned to q->cparams.mtu a bit below, and fq_codel_change() never updates it. codel_should_drop() tests "*backlog <= params->mtu"; with mtu == 0x80000000 (~2 GiB) and the default 32 MiB memory_limit, the test is always true, so CoDel is silently and completely disabled (no drops, no ECN). Declare a single clamped mtu and assign both q->quantum and q->cparams.mtu from it, which also removes the double psched_mtu() call. 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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

Linux — Linux patch: 6.18.52; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <3782067ec0d485628b6f1f9ede3eeeb4f611fcf2; patch: 0; patch: 5.10.270; patch: 5.15.221; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <d9ebd8f9aa8b2773235889cb903fafd61f2d8585; patch: 7.2.6; patch: 6.1.188; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <d315ee8a07fd1810880227319cf60e6cd925ef22; patch: 7.3-rc1; 3.5; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <a9a5b2943a00df2ab81a2209f31dd9e87016f120; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <397e2b1f71d9f15b8b4e47d24eb620e4dff8878d; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <dfb4b61db886917244284b18b44b23d2254b82c2; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <324f86806673ae4a55f66d28db84577f46f615e1; 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe <9f499e5827fdb6d7fdb46a7ce731852f6b1a1bb9; patch: 6.12.110; patch: 6.6.157

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

Linux — Linux

Does this concern one of your customers?

This page cannot answer that — it does not know your estate. Whoever has recorded their environments gets the answer the morning after publication, together with a paragraph they can forward to the customer unedited.

Try it for 28 days

Patchlage reports hits and suspected hits. About everything else this system says nothing — neither this page nor the situation report ever claims that an estate is safe.