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
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