Resource exhaustion in Apache Tomcat
CVE-2026-66299
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.
Vulnerability class: DoS (Denial of Service)
EPSS: 0.005 (43.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
Affected products
- Apache Tomcat — versions 11.0.0
- Apache Software Foundation Tomcat — versions 11.0.0-M20, 10.1.24, 9.0.89
Weakness classification (CWE)
References
- security@apache.org (vendor-advisory, Mailing List, Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-66299?
- CVE-2026-66299 is a medium-severity vulnerability in Apache Tomcat, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-07-28.
- How severe is CVE-2026-66299?
- Medium severity. CVSS v3 base score is 5.3 out of 10.