CVE-2023-53624: net/sched: sch_fq: fix integer overflow of "credit"

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-07 · updated 2026-06-17
Weakness: CWE-190

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_fq: fix integer overflow of "credit" if sch_fq is configured with "initial quantum" having values greater than INT_MAX, the first assignment of "credit" does signed integer overflow to a very negative value. In this situation, the syzkaller script provided by Cristoph triggers the CPU soft-lockup warning even with few sockets. It's not an infinite loop, but "credit" wasn't probably meant to be minus 2Gb for each new flow. Capping "initial quantum" to INT_MAX proved to fix the issue. v2: validation of "initial quantum" is done in fq_policy, instead of open coding in fq_change() _ suggested by Jakub Kicinski

Affected products

Linux kernel: from 3.12 before 5.10.180; from 5.11 before 5.15.111; from 5.16 before 6.1.28; from 6.2 before 6.2.15; from 6.3 before 6.3.2 — fixed in 5.10.180, 5.15.111, 6.1.28, 6.2.15, 6.3.2

How to fix

Upgrade to a fixed version: Linux kernel 5.10.180, 5.15.111, 6.1.28, 6.2.15. Check the vendor advisory for mitigations.

References

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