Apache Tomcat: HTTP/2 header handling DoS

Summary

Denial of Service due to improper input validation vulnerability for HTTP/2 requests in Apache Tomcat. When processing an HTTP/2 request, if the request exceeded any of the configured limits for headers, the associated HTTP/2 stream was not reset until after all of the headers had been processed.This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.0-M16, from 10.1.0-M1 through 10.1.18, from 9.0.0-M1 through 9.0.85, from 8.5.0 through 8.5.98. Other, older, EOL versions may also be affected. Users are recommended to upgrade to version 11.0.0-M17, 10.1.19, 9.0.86 or 8.5.99 which fix the issue.

Timeline

1. Mar 13, 2024, 3:46 PM UTCCVE published
2. Mar 15, 2024, 3:00 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Oct 29, 2025, 11:56 AM UTCRecord last updated
4. Oct 28, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• Apache Software Foundation Apache Tomcat

  From 11.0.0-M1 · through 11.0.0-M16; From 10.1.0-M1 · through 10.1.18; From 9.0.0-M1 · through 9.0.85; From 8.5.0 · through 8.5.98

• org.apache.tomcat:tomcat-coyoteMaven

  From 11.0.0-M1 · fixed in 11.0.0-M17

• org.apache.tomcat:tomcat-coyoteMaven

  From 10.1.0-M1 · fixed in 10.1.19

• org.apache.tomcat:tomcat-coyoteMaven

  From 9.0.0-M1 · fixed in 9.0.86

• org.apache.tomcat:tomcat-coyoteMaven

  From 8.5.0 · fixed in 8.5.99

• org.apache.tomcat.embed:tomcat-embed-coreMaven

  From 8.5.0 · fixed in 8.5.99

• org.apache.tomcat.embed:tomcat-embed-coreMaven

  From 9.0.0-M1 · fixed in 9.0.86

• org.apache.tomcat.embed:tomcat-embed-coreMaven

  From 10.1.0-M1 · fixed in 10.1.19

• org.apache.tomcat.embed:tomcat-embed-coreMaven

  From 11.0.0-M1 · fixed in 11.0.0-M17

References 3