Ubuntu 16.04 & 18.04 Critical Kernel Advisory: Azure Systems Impacted

If exploited, these vulnerabilities could result in downtime or unauthorized access to sensitive information, among other serious security risks for affected systems.

In this article, I'll explore these Ubuntu vulnerabilities and their impact, how to identify which Ubuntu version you are running, and how to update your systems to protect against these flaws. I'll also discuss strategies for mitigating risk.

Understanding These Vulnerabilities

Canonical's updates address multiple vulnerabilities in the Linux kernel for Azure environments. Here are the critical vulnerabilities that were patched:

CVE-2021-33631 (CVSS v3 Severity Score: 7.8 High):

• Description: The ext4 file system implementation was found to validate the data state on miswrite operations.
• Impact: An attacker could exploit this vulnerability by crafting a malicious ext4 file system image. Upon mounting, it could crash the system, resulting in a denial of service.

CVE-2023-6270 (CVSS v3 Severity Score: 7.0 High):

• Description: A race condition in the ATA over Ethernet (AoE) driver was discovered, leading to a use-after-free vulnerability.
• Impact: This could be exploited to cause a denial of service or execute arbitrary code.

CVE-2024-2201:

• Description: Researchers found insufficiencies in mitigations for the initial Branch History Injection vulnerability (CVE-2022-0001) in Intel processors.
• Impact: This could allow local attackers to expose sensitive information.

CVE-2024-23307 (CVSS v3 Severity Score: 7.8 High):

• Description: A race condition in the software RAID driver leads to an integer overflow vulnerability.
• Impact: Privileged attackers could use this to cause a denial of service.

CVE-2024-24861 (CVSS v3 Severity Score: 6.3 Medium):

• Description: A race condition in the Xceive XC4000 silicon tuner device driver led to an integer overflow vulnerability.
• Impact: This could potentially allow an attacker to cause a denial of service.

Other patched vulnerabilities affect several subsystems, including the block layer subsystem, hardware random number generator core, GPU drivers, AFS file system, memory management, and Netfilter. 

Which Ubuntu Versions Are Impacted & What Is the Impact on Affected Systems?

These vulnerabilities primarily impact Ubuntu 16.04 ESM and Ubuntu 18.04 ESM.

Admins running these versions should immediately patch their systems to mitigate the risks associated with the identified vulnerabilities.

The potential consequences of these vulnerabilities are severe:

• Denial of service (DoS) due to system crashes or resource exhaustion.
• Exposure of sensitive information through the exploitation of information disclosure vulnerabilities.
• Execution of arbitrary code could compromise the integrity and security of the system.

How Can I Check My Ubuntu Version?

System administrators can check their Ubuntu version to determine if they are at risk by executing:

lsb_release -a

Alternatively, they can use:

cat /etc/lsb-release

Both commands will provide detailed information about the Ubuntu distribution and release.

How Can I Update My System?

Follow the steps outlined below to update your Ubuntu system and apply the necessary patches.

Update Package List:

sudo apt update

Upgrade Installed Packages:

sudo apt upgrade

Reboot System:

sudo reboot

Consistent updates ensure your system maintains optimal security by applying the latest patches.

EOL Ubuntu Versions: Risks and Mitigation Strategies

The risks of using End-of Life (EOL) Ubuntu versions such as Ubuntu 16.04 or 18.04, without Extended Security Maintenance are significant. These systems are not updated with security patches, making them vulnerable to known exploits.

Practical mitigation strategies admins should implement to reduce risk include:

• Extended Security Maintenance (ESM): ESM is a type of security maintenance that can help reduce the risk of running EOL versions of Ubunto by providing extended support and security protection.
• Subscribe to Ubuntu Pro: This will provide ESM support and extend security updates past the five-year standard period.
• Extended Lifecycle Support: This cost-effective option for ESM offers security patches for Ubuntu 16.04 or 18.04 for five additional years after the end of life. 
• Live Kernel Patching: Live patching solutions allow for live kernel patching. Security updates can be applied without requiring a restart.
• Monitor CVE Trackers Regularly: CVE trackers are a great way to stay current on the latest Linux vulnerabilities and patches.

These best practices can help Linux administrators mitigate risk and maintain a robust security posture, even when Ubuntu versions are no longer supported. 

Our Final Thoughts on Mitigating These Threats

Addressing these Linux kernel flaws in Ubuntu is essential, especially within Microsoft Azure Cloud environments. Administrators can protect their infrastructure from potential threats by taking proactive measures such as using ELS and ESM, patching the kernel, and subscribing to LinuxSecurity newsletters to stay informed of the latest threats to their systems.