Log4J Zero-Day Vulnerability On Friday, December 10, 2021, the world found out about vulnerability CVE-2021-44228 in the Log4J Java component. That component is commonly installed on Web servers and Java application-based systems and servers to log or write system messages and other messages to the computer. This particular vulnerability has been rated a 10.0 out of 10.0 regarding the dangerous abilities that this vulnerability poses to computer systems and its ease of being exploited.