Apache Tomcat Improper Handling of Exceptional Conditions Vulnerability - CVE-2021-30639

A vulnerability in Apache Tomcat allows an attacker to remotely trigger a denial of service. An error introduced as part of a change to improve error handling during non-blocking I/O meant that the error flag associated with the Request object was not reset between requests. This meant that once a non-blocking I/O error occurred all future requests handled by that request object would fail. Users were able to trigger non-blocking I/O errors e.g. by dropping a connection thereby creating the possibility of triggering a DoS. Applications that do not use non-blocking I/O are not exposed to this vulnerability. This issue affects Apache Tomcat 10.0.3 to 10.0.4 9.0.44 8.5.64.