CVE-2023-3611: Out-of-bounds write in Linux kernel's net/sched: sch_qfq component

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-07-21 · updated 2026-10-14
Weakness: CWE-787

Description

An out-of-bounds write vulnerability in the Linux kernel's net/sched: sch_qfq component can be exploited to achieve local privilege escalation. The qfq_change_agg() function in net/sched/sch_qfq.c allows an out-of-bounds write because lmax is updated according to packet sizes without bounds checks. We recommend upgrading past commit 3e337087c3b5805fe0b8a46ba622a962880b5d64.

Affected products

Debian Linux: 10.0, 11.0, 12.0
Linux kernel: from 3.8 before 4.14.322; from 4.15 before 4.19.291; from 4.20 before 5.4.253; from 5.5 before 5.10.188; from 5.11 before 5.15.121; from 5.16 before 6.1.40 — fixed in 4.14.322, 4.19.291, 5.10.188, 5.15.121, 5.4.253, 6.1.40

How to fix

Upgrade to a fixed version: Linux kernel 4.14.322, 4.19.291, 5.10.188, 5.15.121. Check the vendor advisory for mitigations.

References

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