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CVE-2023-4921

7.8 · HIGH

A use-after-free vulnerability in the Linux kernel's net/sched: sch_qfq component can be exploited to achieve local privilege escalation.

Published Sep 12, 2023CWE-416EPSS 0.42%

Overview

CVE-2023-4921 is a high-severity vulnerability. It was published on September 12, 2023 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8fc134fee27f2263988ae38920bc03da416b03d8Refkernel.dance/8fc134fee27f2263988ae38920bc03da416b03d8Reflists.debian.org/debian-lts-announce/2023/10/msg00027.htmlReflists.debian.org/debian-lts-announce/2024/01/msg00004.htmlRefgit.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8fc134fee27f2263988ae38920bc03da416b03d8Refkernel.dance/8fc134fee27f2263988ae38920bc03da416b03d8Reflists.debian.org/debian-lts-announce/2023/10/msg00027.htmlReflists.debian.org/debian-lts-announce/2024/01/msg00004.html

How CyberStrike helps

Frequently asked questions

What is CVE-2023-4921?

CVE-2023-4921 is a high-severity vulnerability. It was published on September 12, 2023 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2023-4921?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2023-4921?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2023-4921?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2023-4921 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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