CVE-2026-66299
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Uncontrolled Resource Consumption in Apache Tomcat WebSocket Example

Publication date: 2026-07-28

Last updated on: 2026-07-28

Assigner: Apache Software Foundation

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.

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Meta Information

Published
2026-07-28
Last Modified
2026-07-28
Generated
2026-07-28
AI Q&A
2026-07-28
EPSS Evaluated
N/A
NVD
CVE-2026-66299
EUVD
EUVD-2026-49855

Affected Vendors & Products

Showing 6 associated CPEs
Vendor Product Version / Range
apache tomcat From 11.0.0-m20 (inc) to 11.0.24 (inc)
apache tomcat From 10.1.24 (inc) to 10.1.57 (inc)
apache tomcat From 9.0.89 (inc) to 9.0.120 (inc)
apache tomcat 11.0.25
apache tomcat 10.1.58
apache tomcat 9.0.121

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.

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Executive Summary

This is an Uncontrolled Resource Consumption vulnerability in Apache Tomcat's WebSocket chat example. It allows an attacker to consume excessive server resources by exploiting the chat example, potentially leading to denial of service.

Detection Guidance

Check if the Tomcat examples web application is deployed by verifying the presence of the /examples/ path in your Tomcat webapps directory. If deployed, inspect logs for unusual WebSocket connection attempts or resource spikes.

Impact Analysis

If you are running an affected version of Apache Tomcat with the examples web application deployed, an attacker could exploit this to consume server resources, causing performance degradation or a crash. Removing the examples web application mitigates the risk.

Mitigation Strategies

Remove the examples web application from your Tomcat installation. Alternatively, upgrade Tomcat to version 11.0.25, 10.1.58, or 9.0.121 (when available) to patch the vulnerability.

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