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.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2020-11996 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (10.0.0-M5, 9.0.35, 8.5.55); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2020-11996? CVE-2020-11996 is a high-severity uncontrolled resource consumption vulnerability in org.apache.tomcat:tomcat (maven), affecting versions >= 10.0.0-M1, <= 10.0.0-M4. It is fixed in 10.0.0-M5, 9.0.35, 8.5.55. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2020-11996? CVE-2020-11996 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2020-11996?
   • org.apache.tomcat:tomcat (maven) (versions >= 10.0.0-M1, <= 10.0.0-M4)
   • org.apache.tomcat.embed:tomcat-embed-core (maven) (versions >= 10.0.0-M1, <= 10.0.0-M4)
4. Is there a fix for CVE-2020-11996? Yes. CVE-2020-11996 is fixed in 10.0.0-M5, 9.0.35, 8.5.55. Upgrade to this version or later.
5. Is CVE-2020-11996 exploitable, and should I be worried? Whether CVE-2020-11996 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-11996 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-11996?
   • Upgrade org.apache.tomcat:tomcat to 10.0.0-M5 or later
   • Upgrade org.apache.tomcat:tomcat to 9.0.35 or later
   • Upgrade org.apache.tomcat:tomcat to 8.5.55 or later
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 10.0.0-M5 or later
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 9.0.35 or later
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 8.5.55 or later