The log4j vulnerability was discovered as a zero-day exploit in late 2021. It’s affected everyone from Amazon Web Services and Cisco to VMware. A log4j security flaw creates a remote code execution vulnerability that hackers can use to execute malicious code.  

This guide will walk you through everything from web application security testing for log4j vulnerabilities to how to secure an app from the attacks they can cause. 

Your team should know these basics of Apache log4j security vulnerabilities and how you can patch them. 

What Is The log4j Vulnerability?

Log4j vulnerabilities in applications were first discovered on November 24th, of 2021 and have become one of the most serious threats since then. The log4j vulnerability attacks a fundamental feature of today’s most popular logging tool. 

Apache log4j 2 is an error logging library used by everything from Amazon to Microsoft. The basics of a log4j attack involve a hacker using text messaging to gain remote control over a system through Apache log4j 2. This allows hackers to execute arbitrary code inside your web application. 

Why Is log4j So Serious? 

There are several reasons why log4j is recognized as one of the most serious security threats in today’s cybersecurity landscape. It’s very difficult to locate log4j vulnerabilities without scanning systems from the inside, meaning that common internet-based security solutions are less effective. Apache log4j 2 is also present in countless web applications which makes this remote code execution vulnerability a potential hazard for millions of users. 

The full picture of the log4j vulnerability is still unfolding. Apache continues to release patches and updates for security risks in log4j. Hackers used the log4j vulnerabilities to fingerprint systems and gain dangerous insight into how web applications function. This means that the ongoing damage from the log4j vulnerability will keep unfolding over time. 

Even if your application doesn’t use Apache’s log4j, a third-party application you rely on most likely does. The impact of log4j can’t be understated. This is a major risk that should be tackled sooner rather than later. 

How Apache log4j Security Vulnerabilities Work

Hackers use the log4j vulnerability in applications to execute remote code execution attacks. These can be used to steal your user’s data or even lock your team out of applications. Hackers can also use the log4j security risk to study your system for more actionable vulnerabilities. 

Hackers start their attacks by scanning your systems for vulnerabilities. Once an opening is found, they can then inject code into Apache log4j 2 and the error logger will attempt to resolve the malicious text. 

Hackers will then build greater access to your systems. This is done using a variety of packages that are designed to trick your application into accepting external, unsanitized, data. Once this stage of the attack is complete, hackers can then execute any code they wish from within your application or server. 

White Hat hackers often use this opportunity to launch the calculator app on vulnerable devices. It’s a rather benign ultimate goal, but if they can launch a calculator, they can feasibly launch any program on that device—or any program they install on that device. 

How Can You Locate log4j Vulnerabilities?

It’s a little tricky to locate log4j vulnerabilities. Apache log4j 2 is built into web applications. This makes it difficult to spot log4j vulnerabilities using scans that see your web app from the “outside” like black box scans. This is why an internal vulnerability scan is vital for finding log4j vulnerabilities. 

A software management tool or a patch management tool are excellent choices for finding log4j vulnerabilities in your application. These tools can check your application against the growing list of applications and components known to be exposed to log4j vulnerabilities. 

This illustrates the importance of white box testing. Web application security teams look for these types of vulnerabilities when testing your application from the inside. A white box test run by cybersecurity experts can be one of the fastest ways to discover and enumerate log4j vulnerabilities in your web app. 

Web Application Security Testing and log4j 

The log4j vulnerability became such a high profile threat due to its presence in millions of devices and the ease with which hackers can execute a remote code execution attack using this exploitation. Web application security testing is your best defense against this incredibly common threat. 

External web application testing is a powerful tool in your overall security plan. Outside cybersecurity experts can see your web application from a fresh perspective. They can also use their insights into web application security to keep your app safe from threats that your team might not have on their radar. 

Web application security testing should be done as an integral part of the development process. Development teams have been increasingly moving their security efforts earlier and earlier in the development process. This is known as “shift-left” in web application security. 

This moves security risks away from your end-users and helps teams tackle security concerns before they become too woven into your application’s design and costly to resolve. 

How To Secure An App From A log4j Vulnerability 

Apache log4j security vulnerabilities have so far been largely used to fingerprint exploited systems, but this easily opens up a remote code execution vulnerability and other threats. Knowing how to secure an app is the key to protecting your business. 

The first step is to identify a log4j vulnerability in your web application. This is best done using the testing methods we mentioned earlier. These include scanning tools that search your application and code for vulnerable flaws. 

Protecting your web application from log4j vulnerabilities starts with recognizing that log4j payloads are a common way for hackers to exploit these vulnerabilities. Web application firewall rules can be configured to deny log4j payloads. You can set default-deny policies that prevent data egress from your systems and limit callbacks to a hacker’s hardware. 

A key step in protecting your systems from log4j vulnerabilities is making sure you update third-party systems. Apache has pushed several security updates and patches for log4j since this vulnerability was discovered. Updating your systems will shut hackers out from everything outside of zero-day exploits.