CVE-2025-53506: Apache Tomcat

High severity, CVSS 7.5. EPSS: 2% chance of exploitation in the next 30 days.

Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106. The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 through 8.5.100. Other EOL versions may also be affected. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.

Affected products

• Apache Tomcat: from 9.0.0, up to and including 9.0.106; from 10.1.0, up to and including 10.1.42; from 11.0.0, up to and including 11.0.8

Published 2025-07-10. Last modified 2026-06-17.