Description
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 API's blocking I/O, clients were able to cause server-side threads to block eventually leading to thread exhaustion and a DoS.
Remediation
References
https://security.netapp.com/advisory/ntap-20190419-0001/
https://support.f5.com/csp/article/K17321505
http://lists.opensuse.org/opensuse-security-announce/2019-06/msg00090.html
http://www.securityfocus.com/bid/107674
https://access.redhat.com/errata/RHSA-2019:3929
https://access.redhat.com/errata/RHSA-2019:3931
https://www.debian.org/security/2019/dsa-4596
https://seclists.org/bugtraq/2019/Dec/43
https://www.oracle.com/security-alerts/cpujan2020.html
https://www.oracle.com/security-alerts/cpuapr2020.html
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00054.html
https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00013.html
https://lists.apache.org/thread.html/e1b0b273b6e8ddcc72c9023bc2394b1276fc72664144bf21d0a87995%40%3Cannounce.tomcat.apache.org%3E
https://lists.apache.org/thread.html/88855876c33f2f9c532ffb75bfee570ccf0b17ffa77493745af9a17a%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/e85e83e9954f169bbb77b44baae5a33d8de878df557bb32b7f793661%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/1dd0a59c1295cc08ce4c9e7edae5ad2268acc9ba55adcefa0532e5ba%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/6af47120905aa7d8fe12f42e8ff2284fb338ba141d3b77b8c7cb61b3%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/e56886e1bac9319ecce81b3612dd7a1a43174a3a741a1c805e16880e%40%3Ccommits.tomee.apache.org%3E
https://lists.apache.org/thread.html/9fe25f98bac6d66f8a663a15c37a98bc2d8f8bbed1d408791a3e4067%40%3Cusers.tomcat.apache.org%3E
https://lists.apache.org/thread.html/4c438fa4c78cb1ce8979077f668ab7145baf83e7c59f2faf7eccf094%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/cf4eb2bd2083cebb3602a293c653f9a7faa96c86f672c876f25b37ef%40%3Cannounce.apache.org%3E
https://lists.apache.org/thread.html/df1a2c1b87c8a6c500ecdbbaf134c7f1491c8d79d98b48c6b9f0fa6a%40%3Cannounce.tomcat.apache.org%3E
https://lists.apache.org/thread.html/158ab719cf60448ddbb074798f09152fdb572fc8f781e70a56118d1a%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/e87733036e8c84ea648cdcdca3098f3c8a897e2652c33062b2b1535c%40%3Cusers.tomcat.apache.org%3E
https://lists.apache.org/thread.html/a7a201bd23e67fd3326c9b22b814dd0537d3270b3b54a768e2e7ef50%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/dddb3590bac28fbe89f69f5ccbe26283d014ddc691abdd042de14600%40%3Cannounce.tomcat.apache.org%3E
https://lists.apache.org/thread.html/7bb193bc68b28d21ff1c726fd38bea164deb6333b59eec2eb3661da6%40%3Cusers.tomcat.apache.org%3E
https://lists.apache.org/thread.html/ac0185ce240a711b542a55bccf9349ab0c2f343d70cf7835e08fabc9%40%3Cannounce.apache.org%3E
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQTZ5BJ5F4KV6N53SGNKSW3UY5DBIQ46/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NPHQEL5AQ6LZSZD2Y6TYZ4RC3WI7NXJ3/
https://lists.apache.org/thread.html/r6ccee4e849bc77df0840c7f853f6bd09d426f6741247da2b7429d5d9%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/r3bbb800a816d0a51eccc5a228c58736960a9fffafa581a225834d97d%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/raba0fabaf4d56d4325ab2aca8814f0b30a237ab83d8106b115ee279a%40%3Cdev.tomcat.apache.org%3E
https://lists.apache.org/thread.html/r48c1444845fe15a823e1374674bfc297d5008a5453788099ea14caf0%40%3Cdev.tomcat.apache.org%3E
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