CVE-2023-6121 Explained : Impact and Mitigation

This CVE record was published by Red Hat and pertains to a vulnerability in the NVMe-oF/TCP subsystem in the Linux kernel. The vulnerability could allow a remote attacker to trigger a heap-based buffer overflow through a crafted TCP packet, potentially leading to the leakage of kmalloc data to the kernel ring buffer (dmesg).

Understanding CVE-2023-6121

This section delves deeper into the nature of CVE-2023-6121, its impact, technical details, affected systems, and mitigation strategies.

What is CVE-2023-6121?

CVE-2023-6121 is an out-of-bounds read vulnerability discovered in the NVMe-oF/TCP subsystem within the Linux kernel. The issue could be exploited by a remote attacker by sending a specifically crafted TCP packet, resulting in a heap-based buffer overflow.

The Impact of CVE-2023-6121

The impact of this vulnerability is categorized as medium severity with a CVSS base score of 4.3. It primarily affects systems running Linux kernel versions susceptible to the NVMe-oF/TCP subsystem exploit.

Technical Details of CVE-2023-6121

This section presents a detailed overview of the vulnerability, including its description, affected systems and versions, and the exploitation mechanism.

Vulnerability Description

The vulnerability in the NVMe-oF/TCP subsystem allows for an out-of-bounds read, potentially leading to a heap-based buffer overflow when a malicious TCP packet is sent remotely.

Affected Systems and Versions

The vulnerability impacts various versions of the Linux kernel, particularly affecting Red Hat Enterprise Linux versions 6, 7, 8, and 9, as well as Fedora systems.

Exploitation Mechanism

The exploitation of CVE-2023-6121 involves sending a specially crafted TCP packet to trigger a heap-based buffer overflow, leading to the potential leakage of sensitive data to the kernel ring buffer.

Mitigation and Prevention

To address CVE-2023-6121, immediate steps should be taken to secure affected systems and prevent potential exploitation.

Immediate Steps to Take

Mitigate the vulnerability by restricting unprivileged users from using dmesg with the following kernel parameter settings:

Run:

sudo sysctl -w kernel.dmesg_restrict=1

Make the changes persistent:

echo 'kernel.dmesg_restrict=1' | sudo tee -a /etc/sysctl.conf

Long-Term Security Practices

Enhance the overall security posture of systems by implementing stringent access controls, staying updated on security patches, and conducting regular security audits.

Patching and Updates

Regularly monitor security advisories from Red Hat, Linux kernel updates, and apply patches promptly to safeguard systems against known vulnerabilities like CVE-2023-6121.