CVE-2026-66299: Apache Tomcat

Medium severity, CVSS 5.3. EPSS: 0.6% chance of exploitation in the next 30 days.

Uncontrolled Resource Consumption vulnerability in Apache Tomcat's WebSocket chat example. This issue affects Apache Tomcat: from 11.0.0-M20 through 11.0.24, from 10.1.24 through 10.1.57, from 9.0.89 through 9.0.120. Users who have followed the security guidance to remove the examples web application are not affected by this issue. Users are recommended to remove the examples web application or to upgrade to version 11.0.25, 10.1.58 or 9.0.121 (when released), which fix the issue.

Affected products

• Apache Tomcat: from 9.0.89, before 9.0.121 (fixed in 9.0.121); from 10.1.24, before 10.1.58 (fixed in 10.1.58); from 11.0.1, before 11.0.25 (fixed in 11.0.25); version 11.0.0 only

Published 2026-07-28. Last modified 2026-08-27.