Everything You Need to Know About Apache Log4J

In a year that will be remembered for cyberattacks, the Apache Log4J, or Log4Shell, zero-day vulnerability may lead to the biggest series of attacks of them all as we move closer to the new year. 

Apache Log4J is an open-source Java package used to enable logging in many popular applications. There is a vulnerability, identified by the Apache Software Foundation (ASF) as CVE-2021-44228, which is found on popular services including Apple iCloud, Twitter, and Minecraft. Amazon, Cisco, Cloudflare, ElasticSearch, and Red Hat are just a few major manufacturers that include Apache Log4J in their software.

The bug has been assigned a maximum CVSS score of 10, partly due to the enormous attack surface that has been exposed, and partly due to the ease of exploitation (we’ll get there shortly). Log4J is used ubiquitously in software and platforms and is the type of program that can sit in the background of a system without making itself known. 

Adding to the complex nature of this vulnerability is that it is used in numerous applications that involve a client and primary application. Organizations that use the client are vulnerable until their vendor updates both the main application and the client. For those using a legacy application, those updates might never take place.

The vulnerability enables threat actors to completely take over affected servers through remote code execution. Ran Shahor, CEO of HolistiCyber says, “The impact of this vulnerability is great because it becomes trivial for attackers to achieve their goals, be it malicious code execution, ransomware, or data theft. The breadth of systems containing this vulnerability is vast – while the actual mitigation is fairly easy, identifying systems and third-party technologies that contain it will be a major challenge.”

A Simple Exploit

Adding to the nature of the threat is the simplicity with which it can be exploited. The hacker only needs to get the app to log a special string, and the system is compromised. The string, which is small enough to fit in a tweet, is sent to the server. The server then logs the data which contains a malicious payload. 

The vulnerability is triggered by the malicious payload, leading the server to request data from a Java Naming and Directory Interface (JNDI). The malicious server responds with a part to a remote Java class file, which is injected into the server process. This triggers a second stage, allowing the attacker to execute their code at will.

Closing the Vulnerability

ASF has released a patch and recommends upgraded Log4J versions to log4j-2.15.0-rc1. For those that are unable to update the patch, they can close the vulnerability by changing log4j2.formatMsgNoLookups to true by adding:”‐Dlog4j2.formatMsgNoLookups=True” to the JVM command for starting the application. 

To see if your organization has been attacked, examine log files for any services using affected Log4J versions, or get in touch with one of our experts to assist.

Under Attack? Get assistance now

The post Everything You Need to Know About Apache Log4J appeared first on HolistiCyber.

*** This is a Security Bloggers Network syndicated blog from HolistiCyber authored by Leora Pudell. Read the original post at: https://holisticyber.com/blog/everything-you-need-to-know-about-apache-log4j/