CVE-2026-77791: Apache Software Foundation Apache Tomcat

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

Uncontrolled Resource Consumption vulnerability in Apache Tomcat during sending of WebSocket close message enabled a DoS attack. This issue affects Apache Tomcat: from 11.0.0-M5 through 11.0.25, from 10.1.8 through 10.1.59, from 9.0.74 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.88 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

Affected products

• Apache Software Foundation Apache Tomcat: from 11.0.0-M5, up to and including 11.0.25; from 10.1.8, up to and including 10.1.59; from 9.0.74, up to and including 9.0.121; from 8.5.88, up to and including 8.5.100

Published 2026-09-23. Last modified 2026-09-23.