CVE-2023-2236 Explained : Impact and Mitigation

This article discusses CVE-2023-2236, a use-after-free vulnerability in the Linux kernel's io_uring subsystem that allows for local privilege escalation.

Understanding CVE-2023-2236

CVE-2023-2236 is a security vulnerability in the Linux Kernel's Performance Events subsystem that enables attackers to escalate their privileges locally.

What is CVE-2023-2236?

The vulnerability arises from a use-after-free flaw within the Linux Kernel's io_uring subsystem. Specifically, the issue occurs when both io_install_fixed_file and its callers invoke fput in a file during an error, resulting in a reference underflow that leads to a use-after-free vulnerability.

The Impact of CVE-2023-2236

This vulnerability, identified as CAPEC-233 Privilege Escalation, poses a significant risk as it allows an attacker to exploit the system and elevate their privileges locally, potentially leading to unauthorized access and control over sensitive information.

Technical Details of CVE-2023-2236

The vulnerability is classified with a base severity rating of HIGH and a CVSS v3.1 base score of 7.8. It has a low attack complexity and vector, with a high impact on confidentiality, integrity, and availability of the affected system. The vulnerability requires low privileges for exploitation and does not involve user interaction.

Vulnerability Description

The use-after-free vulnerability in the Linux Kernel's io_uring subsystem can be exploited by attackers to achieve local privilege escalation by manipulating the system's behavior post-error.

Affected Systems and Versions

The Linux Kernel versions below 6.1, specifically version 5.19, are affected by this vulnerability. Users operating on these versions are at risk of exploitation and should take immediate action to mitigate the issue.

Exploitation Mechanism

Attackers can exploit this vulnerability by triggering specific error conditions that result in a reference underflow, leading to the use-after-free scenario within the Linux Kernel's io_uring subsystem.

Mitigation and Prevention

To address CVE-2023-2236 and prevent potential exploitation, users and system administrators should implement the following measures:

Immediate Steps to Take

Upgrade the Linux Kernel to a version beyond commit 9d94c04c0db024922e886c9fd429659f22f48ea4, where the vulnerability has been patched.
Monitor security advisories and patches from Linux Kernel repositories and vendors to stay informed about updates and remediation steps.

Long-Term Security Practices

Regularly update and patch the Linux Kernel to the latest stable version to mitigate known vulnerabilities and enhance system security.
Implement secure coding practices and conduct vulnerability assessments to identify and address potential security weaknesses within the system.

Patching and Updates

Users and organizations using affected Linux Kernel versions are strongly advised to apply the necessary patches provided by the official Linux Kernel repository. Regularly checking for updates and applying them promptly is crucial to maintaining a secure and resilient system environment.