The situation involving the log4j ( log4shell ) vulnerability has been rapidly evolving since its release a little over a week ago. A new exploit, CVE-2021-45046, was found which was not covered by the initial 2.15.0 patch. Not long after the 2.16.0 patch was released, another issue was found, CVE-2021-45105, which resulted in the release of 2.17.0. There is clearly a lot going on in the log4j library.

Following December 9th, 2021, the news of a Log4j Remote Code Execution (RCE) vulnerability began to grow (Figure 1). In addition to various malware families that already have utilized this vulnerability and added it to their delivery methods arsenal, more vulnerabilities related to this case were published, making Log4j, once simple Java-based logging utility, “the talk of the internet” these days.

The Log4j vulnerability burst onto the scene just a few weeks ago, but to many defenders it already feels like a lifetime. It has rapidly become one of the top concerns for security teams in 2021, and seems set to remain so for the foreseeable future. The critical details of this threat evolve almost daily, making it a formidable challenge for defenders to keep tabs on the threat and their organizations’ exposure.

The popularity of the Log4j library, coupled with the ease of exploitability and severe potential impact, means Log4Shell’s blast radius is enormous – that’s old news by now. However, what’s being revealed these last few days is not just how popular it is, but how deeply rooted it is in the software we use – and this depth is creating some unique challenges in detecting it.

In our recent webinar, Log4j Log4Shell Vulnerability Explained: All You Need To Know, our Senior Director Security Research expert Shachar Menashe shared information on the security issue and how to detect and remediate it. We are happy to share additional information in the following Q&A, based on the questions raised during the webinar.

Just when the Microsoft Exchange exploit CVE-2021-26855 thought it would win the “Exploit of the year” award, it got unseated by the – still evolving – Log4J exploit just weeks before the end of the year! Had somebody asked Sysadmins in November what Log4J was then I suspect that the majority would have had no idea. It seems that the biggest challenge the Log4J exploit poses for Sysadmins is simply the fact that nobody knows all the places where Log4J is being used.

Due to the recently discovered Log4Shell vulnerability, and to support the tremendous effort being mounted by the community to address it, we are happy to announce that we are increasing the free test limit in Snyk Open Source! This means that any developer, no matter the company or project, can now use Snyk Open Source to find and fix Log4Shell with double the number of free tests, whether it’s within your IDE, your Git repositories, CI environments, or using the Snyk CLI.

Just a few days after CVE-2021-45046 was released and fixed, a third zero-day vulnerability was discovered in Apache Log4j, tracked as CVE-2021-45105. The bug was reported on December 15, 2021, and disclosed on December 18, 2021. This third vulnerability has received a CVSS score of 7.5 out of 10, whereas the first one known as Log4Shell (CVE-2021-44228) received the maximum CVSS score of 10 due to its criticality.

Welcome to Elastic’s Log4j2 vulnerability information hub. Here we will explain what the specific Log4j2 vulnerability is, why it matters, and what tools and resources Elastic is providing to help negate the opportunity for malware exploits, cyberattacks, and other cybersecurity risks stemming from Log4j2.