CVE-2026-90076
CVE CVE-2026-90076EUVD EUVD-2026-81937Published 2026-09-17T16:05:55.000Z
What the advisory describes
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: add overflow bounds to quantum and initial quantum fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 * psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill loop adds 0 to f->credit (which stays <= 0) and goto begin loops forever under the qdisc lock, creating a soft lockup. Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product cannot wrap, then cap the result at 1 << 20, matching the bound already enforced on TCA_FQ_QUANTUM in fq_change(). Conditions to recreate the bug: a device whose MTU (plus hard_header_len) is large enough that 2 * psched_mtu() wraps (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 afe4fd062416b158a8a8538b23adc1930a9b88dc <f6b3e3848a5fca63438984acd6d9eceac80814c1; patch: 6.12.110; patch: 0; afe4fd062416b158a8a8538b23adc1930a9b88dc <d16dac3925be95ad46e986d4b139c9898b6e227f; patch: 7.3-rc1; afe4fd062416b158a8a8538b23adc1930a9b88dc <e35acd56f244d94355f9ab237c2ecc8fba5e6f04; afe4fd062416b158a8a8538b23adc1930a9b88dc <709f34f7c28dc4dd6c40343d101850f11e172312; patch: 6.18.52; 3.12; patch: 7.2.6
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
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