Apache Tomcat: Request header mix-up between HTTP/2 streams

Summary

While investigating bug 64830 it was discovered that Apache Tomcat 10.0.0-M1 to 10.0.0-M9, 9.0.0-M1 to 9.0.39 and 8.5.0 to 8.5.59 could re-use an HTTP request header value from the previous stream received on an HTTP/2 connection for the request associated with the subsequent stream. While this would most likely lead to an error and the closure of the HTTP/2 connection, it is possible that information could leak between requests.

Timeline

1. Dec 3, 2020, 6:30 PM UTCCVE published
2. Oct 8, 2026, 9:06 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 8, 2026, 9:13 PM UTCRecord last updated
4. Oct 22, 2026EPSS reached 10%

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

Affected versions

• Apache Software Foundation Apache Tomcat

  Apache Tomcat 10 10.0.0-M1 to 10.0.0-M9, Apache Tomcat 9 9.0.0-M1 to 9.0.39, Apache Tomcat 8.5 8.5.0 to 8.5.59

• tomcatBitnami

  From 8.5.1 · fixed in 8.5.60; From 9.0.1 · fixed in 9.0.40

• org.apache.tomcat:tomcat-coyoteMaven

  From 10.0.0-M1 · fixed in 10.0.0-M10

• org.apache.tomcat:tomcat-coyoteMaven

  From 9.0.0-M1 · fixed in 9.0.40

• org.apache.tomcat:tomcat-coyoteMaven

  From 8.5.0 · fixed in 8.5.60

References 24