CVE-2023-4623: Debian Linux

High severity, CVSS 7.8. EPSS: 0.3% chance of exploitation in the next 30 days.

A use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component can be exploited to achieve local privilege escalation. If a class with a link-sharing curve (i.e. with the HFSC_FSC flag set) has a parent without a link-sharing curve, then init_vf() will call vttree_insert() on the parent, but vttree_remove() will be skipped in update_vf(). This leaves a dangling pointer that can cause a use-after-free. We recommend upgrading past commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f.

Affected products

• Debian Debian Linux: version 10.0 only
• Linux Linux Kernel: from 2.6.12, before 4.14.327 (fixed in 4.14.327); 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 6.1.53 (fixed in 6.1.53); …

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