How To Scan & Fix The Log4j Vulnerability:
Detection, Remediation, & Prevention

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Author: Jason Firch, MBA / Last Updated: 05/14/2023

Reviewed By: Josh Allen

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You can fix the Log4j vulnerability by updating Log4j to the latest version (2.15.0 or later for CVE-2021-44228 and 2.16.0 or later for CVE-2021-45046) and applying temporary workarounds if immediate updating is not feasible. You should also use the Java Security Manager, restrict external configuration, maintain regular updates for dependencies, and actively monitor logs and network traffic for any indications of suspicious activity using intrusion detection systems and security information and event management tools.

The discovery of critical security vulnerabilities in the widely used Log4j library has sent shockwaves throughout the Java application development community.

This powerful logging tool, despite its popularity, has been found to harbor severe security flaws that put countless systems at risk.

The impact of the Log4j vulnerability, known as CVE-2021-44228 or Log4Shell, has been substantial and continues to pose a significant threat due to many unpatched systems.

Within the first 24 hours of the outbreak, security sensors recorded almost 200,000 attack attempts worldwide.

In this article, we’ll explain how Log4j’s security problems work.

We’ll also give helpful tips on how to protect your applications from these threats while still enjoying the benefits of this useful logging tool.

How The Log4j Exploit Works

The Log4j vulnerability works by exploiting a feature within Log4j that allows log messages to include JNDI references.

Attackers craft malicious log messages containing a JNDI reference pointing to an attacker-controlled server.

When a vulnerable Log4j version processes these messages, it unwittingly triggers a remote code execution by fetching and executing malicious code hosted on the attacker’s server.

This exploit grants the attacker unauthorized access and control over the affected systems, posing a significant security risk.

The impact of this vulnerability is widespread, as Log4j is commonly used in various applications and platforms.

Due to its severity, organizations must urgently update their Log4j libraries to a patched version, implement workarounds, or apply additional security measures to mitigate the risk.

Log4j 1.x: End of Life

Log4j 1.x has reached its end of life, and it is no longer receiving updates or security patches. As a result, it is highly recommended to upgrade to Log4j 2.x to ensure your applications remain secure and up-to-date.

Log4j 2.x: Security Enhancements

Log4j 2.x has introduced several security enhancements, including improved handling of user input and support for various security frameworks. These improvements are essential for mitigating potential vulnerabilities and protecting your applications.

Lookups & User Input

Log4j 2.x now handles user input more securely through Lookups. Lookups are used to evaluate expressions within log messages, potentially exposing sensitive data if not properly managed. Log4j 2.x disables Lookups by default, significantly reducing potential security risks.

Java Security Manager Integration

Log4j 2.x provides seamless integration with the Java Security Manager, enabling granular control over the actions that can be performed by the logging library. This integration helps prevent unauthorized access to system resources and ensures the integrity of your applications.

Steps For Scanning For Log4j Vulnerabilities

Scanning for Log4j vulnerabilities involves several steps to ensure comprehensive detection across your systems and applications.

Here are the key steps to follow:

1. Identify potentially affected systems and applications: Create an inventory of all systems, applications, and services that use Java and might have Log4j as a dependency. This includes internal applications, third-party software, and cloud services.
2. Choose an appropriate scanning tool: Select a vulnerability scanning tool that can detect Log4j vulnerabilities, such as Nmap, Tenable Nessus, Qualys Vulnerability Management, Rapid7 InsightVM, or OpenVAS.
3. Update the scanning tool and plugins: Ensure that the scanning tool and its plugins or script libraries are up-to-date to detect the latest Log4j vulnerabilities accurately.
4. Configure the scanning tool: Configure the scanning tool to target specific systems, applications, and network segments where Log4j vulnerabilities may be present. Adjust scan settings to optimize performance and minimize the impact on system resources.
5. Run the vulnerability scan: Initiate the scanning process and monitor its progress. Scanning tools may take some time to complete, depending on the size and complexity of your network and systems.
6. Analyze the scan results: Once the scan is complete, review the results to identify any Log4j vulnerabilities. The scanning tool will typically provide detailed information about the affected systems, the specific vulnerability detected, and the associated risk level.
7. Implement remediation measures: Take the necessary steps to remediate the identified vulnerabilities, such as updating Log4j to a patched version, applying workarounds, or adjusting system configurations. Re-scan the affected systems to ensure that the vulnerabilities have been resolved.
8. Monitor and maintain: Continuously monitor your systems and applications for new Log4j-related vulnerabilities and other security threats. Regularly update your scanning tools, plugins, and system patches to maintain robust security defenses.

What Scanning Tools Can Detect Log4j?

There are several scanning tools and methods available to detect the Log4j vulnerability in your systems and applications.

Some of these tools include:

Nmap

Nmap is a widely-used, open-source network scanning tool that can help identify vulnerable systems by probing open ports and services. Nmap scripts (NSE) specific to Log4j vulnerability detection have been developed, such as log4j2-scan and log4shell.

Tenable

Nessus is a popular vulnerability scanner that can detect the Log4j vulnerability using its regularly updated plugin library. Ensure that you have the latest plugins to scan for Log4j-related issues.

Qualys

Qualys offers a cloud-based vulnerability management platform that can scan your network, systems, and applications for Log4j vulnerabilities. It provides detailed reports and remediation guidance to address the issue.

Rapid7

Rapid7’s vulnerability management solutions, InsightVM and Nexpose, can scan your infrastructure for Log4j vulnerabilities. They offer real-time vulnerability data and prioritization to help you remediate the issue effectively.

OpenVAS

OpenVAS is an open-source vulnerability scanner that can detect Log4j vulnerabilities with its up-to-date plugin feeds. As a part of the Greenbone Vulnerability Management suite, it offers comprehensive vulnerability scanning and reporting capabilities.

In addition to these scanning tools, it is also essential to regularly review logs, employ intrusion detection systems, and monitor network traffic for any signs of Log4j exploitation.

Fixing The Log4j Vulnerability

Follow the steps below to remediate the log4j vulnerability:

1. Update Log4j to the Latest Version

The most effective mitigation strategy is to update the Log4j library to the latest version.

The Apache Software Foundation has released patches addressing the vulnerability:

• Log4j 2.15.0 or later for CVE-2021-44228
• Log4j 2.16.0 or later for CVE-2021-45046 (an additional vulnerability discovered during the investigation)

2. Apply Temporary Workarounds

If updating Log4j is not immediately feasible, temporary workarounds can be implemented, such as:

• Disabling JNDI lookups by setting the system property log4j2.formatMsgNoLookups to true
• Removing the JndiLookup class from the Log4j jar file

3. Use the Java Security Manager

Integrate the Java Security Manager with your applications to enforce strict security policies. This prevents unauthorized actions and ensures a secure environment for your applications.

4. Limit External Configuration

Log4j 2.x allows for external configuration through various means, including XML, JSON, and YAML files. Limit external configuration to trusted sources and validate any configuration files before applying them to your applications.

5. Regularly Update Dependencies

Keep your Log4j and other dependencies up-to-date to ensure that you are using the latest security patches and enhancements. Regular updates help mitigate vulnerabilities and protect your applications from potential threats.

6. Monitor for Suspicious Activity

Regularly monitor logs and network traffic to detect any signs of exploitation. Utilize intrusion detection systems (IDS) and security information and event management (SIEM) tools for real-time threat detection.

How Do You Find Log4j On Windows?

To find Log4j on Windows systems, you can use the following methods:

• File Explorer search: Open the File Explorer and navigate to the root directory of your system, applications, or services that may use Log4j as a dependency. Use the search functionality in the top-right corner and search for “log4j*.jar” to find all Log4j JAR files.
• Command Prompt search: Open the Command Prompt and navigate to the root directory where you suspect Log4j may be present. Use the following command to search for Log4j JAR files:

dir /s /b log4j*.jar

This command searches for Log4j JAR files in the current directory and all its subdirectories, displaying the results with the full path.

• PowerShell search: Open PowerShell and navigate to the root directory where you suspect Log4j may be present. Use the following command to search for Log4j JAR files:

Get-ChildItem -Path . -Recurse -Filter “log4j*.jar” -File | Select-Object FullName

This command searches for Log4j JAR files in the current directory and all its subdirectories, displaying the results with the full path.

Remember to examine all Java applications and services, including third-party software and cloud services, as they might also contain Log4j dependencies.

Preventing Future Log4j Vulnerabilities

To prevent future Log4j-related issues, you should consider the following strategies:

• Stay informed: Regularly check for updates and news about Log4j and related vulnerabilities. Think of it as staying one step ahead of potential attackers.
• Maintain proper patch management: Keep all your software up-to-date, including libraries like Log4j. This will minimize the chances of having unpatched vulnerabilities in your environment.
• Implement continuous vulnerability management: Establish a formal process for identifying, assessing, and remediating vulnerabilities in your applications and infrastructure. A solid vulnerability management plan is like a strong shield against cyber threats.
• Invest in cyber hygiene: Adopt good cybersecurity practices, such as regular penetration tests, employee training, and endpoint security solutions. This will help reduce your overall attack surface and keep your systems protected.

Frequently Asked Questions

What Is Log4j?

Log4j is an open-source Java-based logging library that has recently gained attention due to a critical vulnerability known as Log4Shell. This flaw allows attackers to execute arbitrary code on vulnerable systems, leading to a wide range of cybersecurity issues, such as malware infections, denial-of-service attacks, and other exploits. Think of Log4j as a digital lock that, unfortunately, can be picked by those with malicious intent.

Which Log4j Versions Are Affected??

The vulnerability affects Log4j versions 2.x up to 2.14.1. Update to Log4j 2.15.0 or later to mitigate the risk.

How do I fix the Log4j vulnerability?

Upgrade to Log4j 2.15.0 or later, disable JNDI lookups, or apply a Java Agent that prevents malicious JNDI lookups.

Who Is At Risk Of Log4j?

Anyone using the affected versions of the Log4j library is at risk, including small businesses, large enterprises, and even individuals. Windows, Linux, and macOS systems can all be affected. This vulnerability is considered a “zero-day” exploit, meaning it was unknown until it was publicly disclosed, leaving many systems exposed to potential attacks. It’s like discovering your house keys have been secretly copied and distributed to burglars.

How Do I Know If I Am Vulnerable To Log4j?

Anyone using the affected versions of the Log4j library is at risk, including small businesses, large enterprises, and even individuals. Windows, Linux, and macOS systems can all be affected. This vulnerability is considered a “zero-day” exploit, meaning it was unknown until it was publicly disclosed, leaving many systems exposed to potential attacks. It’s like discovering your house keys have been secretly copied and distributed to burglars.

Can I use Log4j With Other Logging Frameworks?

Yes, Log4j 2.x provides a flexible API that allows you to integrate with other popular logging frameworks, such as SLF4J, Apache Commons Logging, and java.util.logging.

Are There Any Alternatives To Log4j?

Some popular alternatives to Log4j include Logback, SLF4J, and java.util.logging. These logging frameworks offer various features and capabilities, so it is essential to evaluate which one best suits you.

Are Cloud Services & Platforms At Risk?

Cloud services and platforms may be at risk if they use vulnerable versions of Log4j. Many cloud providers have already taken steps to address the vulnerability, but it is essential to verify the status of your specific services and implement necessary updates or workarounds.

Can The Log4j Vulnerability Affect Non-Java Applications?

While the vulnerability primarily impacts Java-based applications, non-Java applications that use the Log4j library through third-party integrations may also be affected. It is crucial to assess all components of your software stack for potential exposure.