A specially crafted sequence of HTTP/2 requests sent to Apache Tomcat 10.0.0-M1 to 10.0.0-M5, 9.0.0.M1 to 9.0.35 and 8.5.0 to 8.5.55 could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.
Fix
Public exploits 1
- rusakovichma/tomcat-embed-core-9.0.31-CVE-2020-11996 PoC on GitHub
Each line links to the index that lists it, never to exploit code. Exploit-DB's "verified" and a Metasploit rank of good or better count as verified; a PoC-in-GitHub entry is a repository's claim.
Patch, vendor advisory and mitigation references on NVD 2
- https://lists.apache.org/thread.html/r5541ef6b6b68b49f76fc4c45695940116da2bcbe0312ef204a00a2e0%40%3Cannounce.tomcat.apache.org%3E Mailing List, Vendor Advisory
- https://lists.apache.org/thread.html/r5541ef6b6b68b49f76fc4c45695940116da2bcbe0312ef204a00a2e0%40%3Cannounce.tomcat.apache.org%3E Mailing List, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 7.5 · apache, canonical, oracleNVD modified 2026-10-08 22:16
Affected (CPE criteria) 45
cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone1:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone10:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone11:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone12:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone13:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone14:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone15:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone16:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone17:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone18:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone19:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone2:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone20:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone21:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone22:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone23:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone24:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone25:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone26:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone27:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone3:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone4:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone5:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone6:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone7:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone8:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:9.0.0:milestone9:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:10.0.0:milestone1:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:10.0.0:milestone2:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:10.0.0:milestone3:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:10.0.0:milestone4:*:*:*:*:*:*cpe:2.3:a:apache:tomcat:10.0.0:milestone5:*:*:*:*:*:*cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*cpe:2.3:a:oracle:mysql_enterprise_monitor:*:*:*:*:*:*:*:*cpe:2.3:a:oracle:siebel_ui_framework:*:*:*:*:*:*:*:*cpe:2.3:a:oracle:workload_manager:12.2.0.1:*:*:*:*:*:*:*cpe:2.3:a:oracle:workload_manager:18c:*:*:*:*:*:*:*cpe:2.3:a:oracle:workload_manager:19c:*:*:*:*:*:*:*cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*- and 5 more
References 48
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00064.html Mailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00072.html Mailing List, Third Party Advisory
- https://lists.apache.org/thread.html/r2529016c311ce9485e6f173446d469600fdfbb94dccadfcd9dfdac79%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/r3ea96d8f36dd404acce83df8aeb22a9e807d6c13ca9c5dec72f872cd%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r5541ef6b6b68b49f76fc4c45695940116da2bcbe0312ef204a00a2e0%40%3Cannounce.tomcat.apache.org%3E Mailing List, Vendor Advisory
- https://lists.apache.org/thread.html/r5a4f80a6acc6607d61dae424b643b594c6188dd4e1eff04705c10db2%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r6c29801370a36c1a5159679269777ad0c73276d3015b8bbefea66e5c%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r74f5a8204efe574cbfcd95b2a16236fe95beb45c4d9fee3dc789dca9%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r8f3d416c193bc9384a8a7dd368623d441f5fcaff1057115008100561%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r8f7484589454638af527182ae55ef5b628ba00c05c5b11887c922fb1%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r93ca628ef3a4530dfe5ac49fddc795f0920a4b2a408b57a30926a42b%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r9ad911fe49450ed9405827af0e7a74104041081ff91864b1f2546bbd%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/ra7092f7492569b39b04ec0decf52628ba86c51f15efb38f5853e2760%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rb4ee49ecc4c59620ffd5e66e84a17e526c2c3cfa95d0cd682d90d338%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rb820f1a2a02bf07414be12c653c2ab5321fd87b9bf6c5e635c53ff4b%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rc80b96b4b96618b2b7461cb90664a428cfd6605eea9f74e51b792542%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rea65d6ef2e45dd1c45faae83922042732866c7b88fa109b76c83db52%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/ref0339792ac6dac1dba83c071a727ad72380899bde60f6aaad4031b9%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2020/07/msg00010.html Mailing List, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20200709-0002/ Third Party Advisory
- https://usn.ubuntu.com/4596-1/ Third Party Advisory
- https://www.debian.org/security/2020/dsa-4727 Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2021.html Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2020.html Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00064.html Mailing List, Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00072.html Mailing List, Third Party Advisory
- https://lists.apache.org/thread.html/r2529016c311ce9485e6f173446d469600fdfbb94dccadfcd9dfdac79%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/r3ea96d8f36dd404acce83df8aeb22a9e807d6c13ca9c5dec72f872cd%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r5541ef6b6b68b49f76fc4c45695940116da2bcbe0312ef204a00a2e0%40%3Cannounce.tomcat.apache.org%3E Mailing List, Vendor Advisory
- https://lists.apache.org/thread.html/r5a4f80a6acc6607d61dae424b643b594c6188dd4e1eff04705c10db2%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r6c29801370a36c1a5159679269777ad0c73276d3015b8bbefea66e5c%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r74f5a8204efe574cbfcd95b2a16236fe95beb45c4d9fee3dc789dca9%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r8f3d416c193bc9384a8a7dd368623d441f5fcaff1057115008100561%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r8f7484589454638af527182ae55ef5b628ba00c05c5b11887c922fb1%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r93ca628ef3a4530dfe5ac49fddc795f0920a4b2a408b57a30926a42b%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r9ad911fe49450ed9405827af0e7a74104041081ff91864b1f2546bbd%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/ra7092f7492569b39b04ec0decf52628ba86c51f15efb38f5853e2760%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rb4ee49ecc4c59620ffd5e66e84a17e526c2c3cfa95d0cd682d90d338%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rb820f1a2a02bf07414be12c653c2ab5321fd87b9bf6c5e635c53ff4b%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rc80b96b4b96618b2b7461cb90664a428cfd6605eea9f74e51b792542%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rea65d6ef2e45dd1c45faae83922042732866c7b88fa109b76c83db52%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/ref0339792ac6dac1dba83c071a727ad72380899bde60f6aaad4031b9%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2020/07/msg00010.html Mailing List, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20200709-0002/ Third Party Advisory
- https://usn.ubuntu.com/4596-1/ Third Party Advisory
- https://www.debian.org/security/2020/dsa-4727 Third Party Advisory
- https://www.oracle.com/security-alerts/cpujan2021.html Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2020.html Third Party Advisory