CVE-2021-4095 : What You Need to Know

A NULL pointer dereference was found in the Linux kernel's KVM when dirty ring logging is enabled without an active vCPU context, allowing an unprivileged local attacker to trigger a denial of service. This vulnerability affects Linux kernel versions prior to 5.17-rc1.

Understanding CVE-2021-4095

This section provides an overview of the CVE-2021-4095 vulnerability.

What is CVE-2021-4095?

CVE-2021-4095 is a NULL pointer dereference vulnerability in the Linux kernel's KVM that can be exploited by an unprivileged local attacker to cause a denial of service by issuing a specific ioctl.

The Impact of CVE-2021-4095

The impact of CVE-2021-4095 is the potential for a kernel oops condition, leading to a denial of service on the affected system.

Technical Details of CVE-2021-4095

In this section, we delve into the technical details of CVE-2021-4095.

Vulnerability Description

The vulnerability arises in the Linux kernel's KVM module when dirty ring logging is enabled without an active vCPU context, resulting in a NULL pointer dereference.

Affected Systems and Versions

Linux kernel versions prior to 5.17-rc1 are impacted by this vulnerability.

Exploitation Mechanism

An unprivileged local attacker can exploit this vulnerability by issuing a specific ioctl, KVM_XEN_HVM_SET_ATTR, resulting in a kernel oops condition.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-4095, certain steps can be taken.

Immediate Steps to Take

Users are advised to apply relevant security updates provided by the Linux kernel maintainers to address this vulnerability promptly.

Long-Term Security Practices

Implementing least privilege principles and regular security updates can help enhance system security in the long term.

Patching and Updates

Regularly updating the Linux kernel to versions beyond 5.17-rc1 is essential for protecting the system against CVE-2021-4095.