CVE-2023-4921: Debian Linux

High severity, CVSS 7.8. EPSS: 0.4% chance of exploitation in the next 30 days.

A use-after-free vulnerability in the Linux kernel's net/sched: sch_qfq component can be exploited to achieve local privilege escalation. When the plug qdisc is used as a class of the qfq qdisc, sending network packets triggers use-after-free in qfq_dequeue() due to the incorrect .peek handler of sch_plug and lack of error checking in agg_dequeue(). We recommend upgrading past commit 8fc134fee27f2263988ae38920bc03da416b03d8.

Affected products

• Debian Debian Linux: version 10.0 only
• Linux Linux Kernel: from 3.8, before 4.14.326 (fixed in 4.14.326); from 4.15, before 4.19.295 (fixed in 4.19.295); from 4.20, before 5.4.257 (fixed in 5.4.257); from 5.5, before 5.10.195 (fixed in 5.10.195); from 5.11, before 5.15.132 (fixed in 5.15.132); from 5.16, before 6.1.54 (fixed in 6.1.54); …

Published 2023-09-12. Last modified 2026-06-17.