CVE-2026-66299

Apache Tomcat: DoS via WebSocket chat example

Description

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.

Scores

Weaknesses (CWE)

• CWE-400

European references

• ENISA EUVD · EUVD-2026-49855
• GCVE · GCVE-0-2026-66299

CERT-FR advisories

• CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
• CERTFR-2026-AVI-1249 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
• CERTFR-2026-AVI-1083 — Multiples vulnérabilités dans Apache Tomcat · cert.ssi.gouv.fr
• CERTFR-2026-AVI-0940 — Vulnérabilité dans Apache Tomcat · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

• cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* ≥ 9.0.89 < 9.0.121
• cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* ≥ 10.1.24 < 10.1.58
• cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* ≥ 11.0.1 < 11.0.25
• cpe:2.3:a:apache:tomcat:11.0.0:milestone20:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone21:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone22:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone23:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone24:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone25:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:11.0.0:milestone26:*:*:*:*:*:*

Affected products

References

• https://lists.apache.org/thread/8owczcc1o8qw1rxmg9gvfk4w2jnh4l5k
• http://www.openwall.com/lists/oss-security/2026/07/28/25

Sources