Apache Tomcat: WebSocket DoS with incomplete closing handshake

Summary

Denial of Service via incomplete cleanup vulnerability in Apache Tomcat. It was possible for WebSocket clients to keep WebSocket connections open leading to increased resource consumption.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. 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, 3:48 PM UTCCVE published
2. Mar 13, 2024, 6:10 PM UTCCISA SSVC assessment

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

3. Oct 29, 2025, 11:57 AM UTCRecord last updated

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-websocketMaven

  From 11.0.0-M1 · fixed in 11.0.0-M17

• org.apache.tomcat:tomcat-websocketMaven

  From 10.1.0-M1 · fixed in 10.1.19

• org.apache.tomcat:tomcat-websocketMaven

  From 9.0.0-M1 · fixed in 9.0.86

• org.apache.tomcat:tomcat-websocketMaven

  From 8.5.0 · fixed in 8.5.99

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

  From 11.0.0-M1 · fixed in 11.0.0-M17

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

  From 10.1.0-M1 · fixed in 10.1.19

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

  From 9.0.0-M1 · fixed in 9.0.86

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

  From 8.5.0 · fixed in 8.5.99

References 1