Apache Tomcat, a widely used Java HTTP web server environment, has been affected by a high-severity vulnerability known as Ghostcat. The vulnerability was discovered in the Apache JServ Protocol (AJP) and allows an attacker to read or include any file into Tomcat webapp directories. All versions of Tomcat that do not contain the patch are vulnerable, including those using the AJP Connector on port 8009. To mitigate this issue, users can disable the AJP Connector by commenting out or deleting its declaration in the server.xml file, or add a requiredSecret field with a safe secret to the Connector configuration. Spring Boot users should also be aware that they may be vulnerable if they use an embedded Tomcat package without proper configuration.