CVE-2021-0200 is a vulnerability in the Apache Tomcat web server that was discovered in March 2021. The flaw allows an attacker to remotely execute arbitrary code on the affected system without authentication. The vulnerability exists because of a flaw in the implementation of the Tomcat AJP protocol, which can be exploited by sending specially crafted requests to the server.
When the vulnerability was first discovered, the Apache Software Foundation released a security advisory and urged users to upgrade to the latest version of Tomcat immediately. Vulnerability scanners also quickly started detecting the flaw, and it was given a high severity rating by the Common Vulnerability Scoring System (CVSS). The vulnerability affected all versions of Apache Tomcat up to and including version 9.0.45 and required no special configuration to exploit.
In the months since the vulnerability was disclosed, there have been reports of malicious actors actively exploiting the flaw in the wild. In some cases, attackers have used the vulnerability to install cryptominers on vulnerable servers, while in others, they have used it to gain access to sensitive data. Given the severity of the vulnerability and the potential impact of a successful attack, organizations are strongly advised to ensure that they have patched their Apache Tomcat instances to protect against this flaw.