Log4j - Remote Code Execution (Log4Shell - CVE-2021-45046)

Log4j logging library is affected by a Remote Code Execution vulnerability. The root cause of the vulnerability is improper input validation in the JNDI functionality implemented in Apache Log4j <= 2.14.1. A feature called message lookup substitution, which is enabled by default in the affected versions, allows attackers to load and execute arbitrary Java code from a remote LDAP server. Furthermore, multiple protocols are supported in the JNDI lookups, including LDAP, LDAPS, DNS and RMI. Therefore, if an attacker can control the log messages and inject arbitrary code through one of the input parameters or in the HTTP headers, he can create a malicious Java class on a controlled server and the vulnerable server will use the lookup method to execute the Java class from the LDAP/LDAPS/DNS/RMI server. All the versions before 2.17.1 are affected.

The risk exists that a remote unauthenticated attacker can fully compromise the server in order to steal confidential information, install ransomware, or pivot to the internal network.

Upgrade the Log4j library to at least version 2.17.1.