CVE-2023-4623

Name: CVE-2023-4623
Creator: NVD / NIST
Published: 2023-09-06T14:15:12.357+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 0.29%

Last modified Jun 17, 2026

CVE-2023-4623 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. 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(). EPSS estimates a 0.29% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.29%

20.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	>= 2.6.12, < 4.14.327
Linux	Linux Kernel	>= 4.15, < 4.19.295
Linux	Linux Kernel	>= 4.20, < 5.4.257
Linux	Linux Kernel	>= 5.5, < 5.10.195
Linux	Linux Kernel	>= 5.11, < 5.15.132
Linux	Linux Kernel	>= 5.16, < 6.1.53
Linux	Linux Kernel	>= 6.2, < 6.4.16
Linux	Linux Kernel	>= 6.5, < 6.5.3
Debian	Debian Linux	10.0

References

http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.htmlThird Party Advisory, VDB Entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3d26c5702c7d6c45456326e56d2ccf3f103e60fIssue Tracking, Mailing List, Patch, Vendor Advisory
https://kernel.dance/b3d26c5702c7d6c45456326e56d2ccf3f103e60fPatch, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2023/10/msg00027.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2024/01/msg00004.htmlMailing List, Third Party Advisory
http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.htmlThird Party Advisory, VDB Entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3d26c5702c7d6c45456326e56d2ccf3f103e60fIssue Tracking, Mailing List, Patch, Vendor Advisory
https://kernel.dance/b3d26c5702c7d6c45456326e56d2ccf3f103e60fPatch, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2023/10/msg00027.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2024/01/msg00004.htmlMailing List, Third Party Advisory

Timeline

Published: Sep 6, 2023
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2023-4623?

How severe is CVE-2023-4623?

CVE-2023-4623 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.29% probability of exploitation in the next 30 days.

How do I fix CVE-2023-4623?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-4623?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST