Is it possible that Ubuntu is vulnerable to Log4shell?

Introduction

Recently, a new vulnerability called Log4Shell has been discovered in the popular logging library, log4j. This vulnerability allows attackers to execute arbitrary code remotely, which can lead to a full compromise of the affected system. This vulnerability has been rated as critical, and many organizations are rushing to patch their systems to mitigate the risk. In this blog post, we will explore whether Ubuntu is vulnerable to Log4Shell and what steps you can take to protect your systems.

What is Log4Shell?

Log4Shell is a vulnerability that affects the widely used logging framework, log4j. This vulnerability allows attackers to execute arbitrary code remotely, which can lead to a full compromise of the affected system. The vulnerability is caused by an insecure way of handling user-supplied data in the log4j library. Attackers can exploit this vulnerability by sending specially crafted requests to a vulnerable server, which can then execute arbitrary code on the server.

Is Ubuntu vulnerable to Log4Shell?

The short answer is yes. Ubuntu is vulnerable to Log4Shell if you are using log4j in your Ubuntu systems. Many Ubuntu systems use log4j for logging purposes, and this makes them vulnerable to Log4Shell. However, the good news is that not all versions of log4j are vulnerable to Log4Shell. The vulnerability exists in versions of log4j from 2.0-beta9 to 2.15.0. If you are using a version of log4j that is outside this range, your system is not vulnerable to Log4Shell.

How to check if your Ubuntu system is vulnerable to Log4Shell?

You can check if your Ubuntu system is vulnerable to Log4Shell by checking the version of log4j installed on your system. To do this, you can run the following command:

dpkg -l | grep log4j

This command will list all the log4j packages installed on your system. If you are using a version of log4j that is between 2.0-beta9 to 2.15.0, your system is vulnerable to Log4Shell. If you are using a version of log4j that is outside this range, your system is not vulnerable to Log4Shell.

How to protect your Ubuntu system from Log4Shell?

The best way to protect your Ubuntu system from Log4Shell is to upgrade to a version of log4j that is not vulnerable to Log4Shell. If you are using a version of log4j that is between 2.0-beta9 to 2.15.0, you should upgrade to a version of log4j that is outside this range. You can do this by running the following command:

sudo apt-get update
sudo apt-get install liblog4j1.2-java

This command will install the latest version of log4j that is not vulnerable to Log4Shell. After installing the new version of log4j, you should restart your application server to ensure that the new version of log4j is loaded.

Conclusion

Log4Shell is a critical vulnerability that affects the popular logging library, log4j. Ubuntu systems that use log4j for logging purposes are vulnerable to Log4Shell if they are using a version of log4j that is between 2.0-beta9 to 2.15.0. To protect your Ubuntu systems from Log4Shell, you should upgrade to a version of log4j that is not vulnerable to Log4Shell. We hope this blog post has provided you with valuable information on how to protect your Ubuntu systems from Log4Shell.

In general, it is important to keep all software up to date in order to protect against known vulnerabilities. This includes the operating system, as well as any other applications that are installed. You can use the apt-get update and apt-get upgrade commands to update the software on your Ubuntu system. It is also a good idea to keep an eye on security advisories and take appropriate action if a vulnerability is discovered in software that you use.

Software updates are important for several reasons, including:

1. Security: Software updates often include security fixes for vulnerabilities that have been discovered in the software. By keeping your software up to date, you can protect against known vulnerabilities and reduce the risk of being hacked or otherwise exploited.
2. Performance: Software updates can also include performance improvements and bug fixes that can make the software run more smoothly and reliably.
3. New features: Software updates may also include new features or functionality that can enhance the user experience or improve productivity.

It is generally a good practice to keep all software up to date, including the operating system and any applications that are installed. Many software programs have an automatic update feature that can be enabled, which will automatically download and install updates as they become available. It is also a good idea to regularly check for updates manually and install them as needed.

Generally, I cannot say whether I am vulnerable to the Apache Log4j vulnerability unless I have a specific package installed. The deb package, apache-log4j2, is not part of a stock Ubuntu install, so I am most likely not affected. However, if I installed log4j2 as part of my webserver using a Snap package, I should check with the author of that Snap for a security upgrade.

If I installed log4j2 as part of my webserver some other way, such as Appimage, Flatpak, Pip, Brew, or compiled it myself, it is up to me to return to that source and find a patched version or to manually mitigate the issue based on the CVE. Thanks to the hard-working engineers on the Ubuntu Security Team, most affected folks have already received a patch to close the vulnerability.

If I want to confirm whether I am vulnerable, I can ask apt by running the command “apt list apache-log4j2”. Depending on the output, I can determine if I am vulnerable or not. If my system is vulnerable, I should run “sudo apt update” and “sudo apt upgrade” to pull in the latest security upgrades.

If I find a vulnerable snap package, I should file a bug report with the author, as snap confinement is meant to prevent vulnerabilities from threatening the entire system.