Improper Access Control
Apache Tomcat 7.x through 7.0.70 and 8.x through 8.5.4, when the CGI Servlet is enabled, follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue. NOTE: the vendor states "A mitigation is planned for future releases of Tomcat, tracked as CVE-2016-5388"; in other words, this is not a CVE ID for a vulnerability.
Improper Access Control
Remote code execution is possible with Apache Tomcat before 6.0.48, 7.x before 7.0.73, 8.x before 8.0.39, 8.5.x before 8.5.7, and 9.x before 9.0.0.M12 if JmxRemoteLifecycleListener is used and an attacker can reach JMX ports. The issue exists because this listener wasn't updated for consistency with the CVE-2016-3427 Oracle patch that affected credential types.
Improper Input Validation in Apache Tomcat
java/org/apache/catalina/servlets/DefaultServlet.java in the default servlet in Apache Tomcat before 6.0.40, 7.x before 7.0.53, and 8.x before 8.0.4 does not properly restrict XSLT stylesheets, which allows remote attackers to bypass security-manager restrictions and read arbitrary files via a crafted web application that provides an XML external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue.
Incorrect Authorization
The ResourceLinkFactory implementation in Apache Tomcat 9.0.0.M1 to 9.0.0.M9, 8.5.0 to 8.5.4, 8.0.0.RC1 to 8.0.36, 7.0.0 to 7.0.70 and 6.0.0 to 6.0.45 does not limit web application access to global JNDI resources to those resources explicitly linked to the web application. Therefore, it was possible for a web application to access any global JNDI resource whether an explicit ResourceLink had been configured or not.
Missing XML Validation in Apache Tomcat
Apache Tomcat before 6.0.40, 7.x before 7.0.54, and 8.x before 8.0.6 does not properly constrain the class loader that accesses the XML parser used with an XSLT stylesheet, which allows remote attackers to (1) read arbitrary files via a crafted web application that provides an XML external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue, or (2) read files associated with different web applications on a single Tomcat instance via a crafted web application.