Then on December 28th, security researchers at Checkmarx published findings of another RCE present in Log4J 2.17.0, one which requires the attacker have permissions to update the logging configuration and, when successful, can yield RCE. Tracked as CVE-2021-45105 (and with a “high” CVSS score of 7.5), this vulnerability appeared to affect Log4J versions 2.8 through the most recent 2.16.0 release, and was fixed in versions 2.17.0 (for Java 8) and 2.12.3 (for Java 7). While Apache released fixes to CVE-2021-44228 in Log4J version 2.15.0, it was discovered these fixes were “incomplete in certain non-default configurations”, allowing for exploitation in certain circumstances (tracked as CVE-2021-45046 (with a “critical” CVSS core of 9.0), leading to a Log4J 2.16.0 release to address CVE-2021-45046.įollowing that release, a new vulnerability was raised which can yield a denial-of-service attack via infinite recursion.
Unfortunately, a modern version of Java may not be enough to prevent exploitation, as the application itself may expose classes that can be used to run arbitrary code. This path is partially mitigated by the use of newer Java runtimes that block the URL-based class loader by default. The first examples of this used the $ path, which could lead to arbitrary code being loaded from a remote URL. The most significant impact is that an attacker can cause a string to reach the logger, that when processed by Log4J, executes arbitrary code. This issue is widespread because many developers were unaware that Log4J was dangerous to use with unfiltered input. This particular vulnerability - tracked as CVE-2021-44228 with the maximum “critical” CVSS score of 10 - resides in Log4J’s lookup capability, combined with JNDI (Java Naming and Directory Interface). Internet discussion was abuzz on December 9th about an 0-day vulnerability that can yield remote code execution (RCE) in Apache’s popular Log4J logging library for Java. runZero is not a vulnerability scanner, but you can share runZero’s results with your security team for investigation and mitigation. RunZero can help you build an up-to-date asset inventory and search for assets that may be affected by Log4J vulnerabilities, such as Log4shell.
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