CVE-2023-4207: 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: cls_fw component can be exploited to achieve local privilege escalation. When fw_change() is called on an existing filter, the whole tcf_result struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcf_unbind_filter() is always called on the old instance in the success path, decreasing filter_cnt of the still referenced class and allowing it to be deleted, leading to a use-after-free. We recommend upgrading past commit 76e42ae831991c828cffa8c37736ebfb831ad5ec.

Affected products

• Debian Debian Linux: version 12.0 only
• Linux Linux Kernel: from 3.18, 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 5.4.253 (fixed in 5.4.253); from 5.5, before 5.10.190 (fixed in 5.10.190); from 5.11, before 5.15.126 (fixed in 5.15.126); from 5.16, before 6.1.45 (fixed in 6.1.45); …

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