The HTTP/2 implementation in Apache Tomcat 9.0.0.M1 to 9.0.14 and 8.5.0 to 8.5.37 accepted streams with excessive numbers of SETTINGS frames and also permitted clients to keep streams open without reading/writing request/response data. By keeping streams open for requests that utilised the Servlet APIs blocking I/O, clients were able to cause server-side threads to block eventually leading to thread exhaustion and a DoS.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Tomcat | Apache | 8.5.0 (including) | 8.5.37 (including) |
| Tomcat | Apache | 9.0.1 (including) | 9.0.14 (including) |
| Tomcat | Apache | 9.0.0-milestone1 (including) | 9.0.0-milestone1 (including) |
| Tomcat | Apache | 9.0.0-milestone10 (including) | 9.0.0-milestone10 (including) |
| Tomcat | Apache | 9.0.0-milestone11 (including) | 9.0.0-milestone11 (including) |
| Tomcat | Apache | 9.0.0-milestone12 (including) | 9.0.0-milestone12 (including) |
| Tomcat | Apache | 9.0.0-milestone13 (including) | 9.0.0-milestone13 (including) |
| Tomcat | Apache | 9.0.0-milestone14 (including) | 9.0.0-milestone14 (including) |
| Tomcat | Apache | 9.0.0-milestone15 (including) | 9.0.0-milestone15 (including) |
| Tomcat | Apache | 9.0.0-milestone16 (including) | 9.0.0-milestone16 (including) |
| Tomcat | Apache | 9.0.0-milestone17 (including) | 9.0.0-milestone17 (including) |
| Tomcat | Apache | 9.0.0-milestone18 (including) | 9.0.0-milestone18 (including) |
| Tomcat | Apache | 9.0.0-milestone19 (including) | 9.0.0-milestone19 (including) |
| Tomcat | Apache | 9.0.0-milestone2 (including) | 9.0.0-milestone2 (including) |
| Tomcat | Apache | 9.0.0-milestone20 (including) | 9.0.0-milestone20 (including) |
| Tomcat | Apache | 9.0.0-milestone21 (including) | 9.0.0-milestone21 (including) |
| Tomcat | Apache | 9.0.0-milestone3 (including) | 9.0.0-milestone3 (including) |
| Tomcat | Apache | 9.0.0-milestone4 (including) | 9.0.0-milestone4 (including) |
| Tomcat | Apache | 9.0.0-milestone5 (including) | 9.0.0-milestone5 (including) |
| Tomcat | Apache | 9.0.0-milestone6 (including) | 9.0.0-milestone6 (including) |
| Tomcat | Apache | 9.0.0-milestone7 (including) | 9.0.0-milestone7 (including) |
| Tomcat | Apache | 9.0.0-milestone8 (including) | 9.0.0-milestone8 (including) |
| Tomcat | Apache | 9.0.0-milestone9 (including) | 9.0.0-milestone9 (including) |
| Red Hat JBoss Web Server 5 | RedHat | tomcat | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-ecj-0:4.12.0-1.redhat_1.1.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-javapackages-tools-0:3.4.1-5.15.11.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-jboss-logging-0:3.3.2-1.Final_redhat_00001.1.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-mod_cluster-0:1.4.1-1.Final_redhat_00001.2.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-tomcat-0:9.0.21-10.redhat_4.1.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-tomcat-native-0:1.2.21-34.redhat_34.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 6 | RedHat | jws5-tomcat-vault-0:1.1.8-1.Final_redhat_1.1.el6jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-ecj-0:4.12.0-1.redhat_1.1.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-javapackages-tools-0:3.4.1-5.15.11.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-jboss-logging-0:3.3.2-1.Final_redhat_00001.1.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-mod_cluster-0:1.4.1-1.Final_redhat_00001.2.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-tomcat-0:9.0.21-10.redhat_4.1.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-tomcat-native-0:1.2.21-34.redhat_34.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 7 | RedHat | jws5-tomcat-vault-0:1.1.8-1.Final_redhat_1.1.el7jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-ecj-0:4.12.0-1.redhat_1.1.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-javapackages-tools-0:3.4.1-5.15.11.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-jboss-logging-0:3.3.2-1.Final_redhat_00001.1.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-mod_cluster-0:1.4.1-1.Final_redhat_00001.2.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-tomcat-0:9.0.21-10.redhat_4.1.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-tomcat-native-0:1.2.21-34.redhat_34.el8jws | * |
| Red Hat JBoss Web Server 5.2 on RHEL 8 | RedHat | jws5-tomcat-vault-0:1.1.8-1.Final_redhat_1.1.el8jws | * |
| Red Hat Runtimes Spring Boot 2.1.12 | RedHat | tomcat | * |
| Tomcat8 | Ubuntu | bionic | * |
| Tomcat8 | Ubuntu | cosmic | * |
| Tomcat8 | Ubuntu | esm-apps/bionic | * |
| Tomcat8 | Ubuntu | upstream | * |
| Tomcat9 | Ubuntu | upstream | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.