CVE-2020-11996

CVE-2020-11996 is a high-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 27% places it in the 98th percentile, indicating an elevated likelihood of exploitation.

Key facts

• Severity: High (CVSS 3.x base score 7.5)
• CVSS v2: 5.0
• EPSS exploit prediction: 27% (98th percentile)
• Actively exploited: Not listed in CISA KEV
• Affected product: Apache Tomcat
• Published: 2020-06-26
• Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2020-11996?

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.

How severe is CVE-2020-11996?

CVE-2020-11996 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-11996 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 27% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-11996?

CVE-2020-11996 primarily affects Apache Tomcat. In total, 45 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-11996?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-11996 published?

CVE-2020-11996 was published on 2020-06-26 and last updated on 2026-06-17.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00064.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00072.html
• 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
• 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
• https://security.netapp.com/advisory/ntap-20200709-0002/
• https://usn.ubuntu.com/4596-1/
• https://www.debian.org/security/2020/dsa-4727
• https://www.oracle.com/security-alerts/cpujan2021.html
• https://www.oracle.com/security-alerts/cpuoct2020.html

Affected products (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:*:*:*:*:*:*:*

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