CVE-2023-4623 : Security Advisory and Response

This CVE record involves a use-after-free vulnerability found in the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component, with the potential of local privilege escalation. The vulnerability was discovered by Budimir Markovic and has a CVSS base score of 7.8, categorizing it as a high severity issue.

Understanding CVE-2023-4623

This section delves into the details surrounding CVE-2023-4623.

What is CVE-2023-4623?

The vulnerability identified as CVE-2023-4623 exists in the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component. An attacker could exploit this flaw to achieve local privilege escalation. Specifically, the vulnerability occurs when a class with a link-sharing curve (HFSC_FSC flag set) has a parent without a link-sharing curve, leading to a dangling pointer that can trigger a use-after-free situation.

The Impact of CVE-2023-4623

Given the nature of this vulnerability, an attacker could potentially escalate their privileges on a local system, thereby compromising its security integrity. It is crucial to address this issue promptly to prevent any exploitation.

Technical Details of CVE-2023-4623

Explore the technical aspects related to CVE-2023-4623 for a better understanding.

Vulnerability Description

The use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component arises due to the improper handling of parent-child relationships involving link-sharing curves. This can result in a dangling pointer scenario, leading to potential exploitation for privilege escalation.

Affected Systems and Versions

The vulnerability impacts systems running the Linux Kernel with versions starting from 2.6.12 up to versions less than 6.6 that utilize the custom versioning scheme. It is important to note that this vulnerability affects these specific configurations and versions.

Exploitation Mechanism

Exploiting this vulnerability involves manipulating the parent-child relationships in the context of link-sharing curves within the HFSC qdisc traffic control component of the Linux kernel. By creating a situation where vttree_remove() is skipped in update_vf(), an attacker could potentially trigger a use-after-free scenario.

Mitigation and Prevention

To secure systems and mitigate the risks associated with CVE-2023-4623, certain measures need to be taken promptly.

Immediate Steps to Take

Upgrade systems past commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f to address the use-after-free vulnerability.
Implement relevant security patches provided by the Linux kernel maintainers to remediate the issue.

Long-Term Security Practices

Regularly update and patch the Linux kernel to incorporate the latest security fixes and enhancements.
Monitor security advisories and CVE reports to stay informed about potential vulnerabilities affecting the system.

Patching and Updates

Stay informed about security updates released by the Linux kernel community.
Apply patches promptly to ensure that the system is protected against known vulnerabilities.

By following these mitigation strategies and maintaining proactive security practices, organizations can safeguard their systems against potential risks posed by CVE-2023-4623.