Vulnerability · Published Jul 28, 2026 · Assigned by apache
CVE-2026-66299Apache Tomcat: DoS via WebSocket chat example
High 7.5
In plain English
A high-severity uncontrolled resource consumption in Apache Tomcat from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 46% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | tomcat10 | no fix listed | DEBIAN-CVE-2026-66299 |
| Debian:13 | tomcat10 | no fix listed | DEBIAN-CVE-2026-66299 |
| Debian:14 | tomcat10 | 10.1.60-1 | DEBIAN-CVE-2026-66299 |
| Debian:13 | tomcat11 | no fix listed | DEBIAN-CVE-2026-66299 |
| Debian:14 | tomcat11 | no fix listed | DEBIAN-CVE-2026-66299 |
| Debian:12 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-66299 |
| Debian:13 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-66299 |
| Debian:14 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-66299 |
| Ubuntu:24.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.10 | tomcat10 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.04:LTS | tomcat11 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.10 | tomcat11 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:24.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-66299 |
| Ubuntu:26.10 | tomcat9 | no fix listed | UBUNTU-CVE-2026-66299 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Tomcat | 11.0.0-M20 – through 11.0.2410.1.24 – through 10.1.579.0.89 – through 9.0.120 |
Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H