Allocation of Resources Without Limits or Throttling in Apache Tomcat - CVE-2026-66299

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Main Vulnerability Database Vulnerabilities #VU139938

Allocation of Resources Without Limits or Throttling in Apache Tomcat - CVE-2026-66299

Published: July 28, 2026 / Updated: August 25, 2026


Vulnerability identifier: #VU139938
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-66299
CWE-ID: CWE-770
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper resource management in the WebSocket chat example when buffering undelivered messages for a maliciously slow client connection. A remote attacker can maintain a slow client connection to cause a denial of service.

Only deployments exposing the example web application are vulnerable.


Affected software

Apache Tomcat
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
Web and Scripting Module
openSUSE Leap
openEuler
tomcat-help
tomcat-jsvc
tomcat
tomcat-servlet-4_0-api
tomcat-lib
tomcat-admin-webapps
tomcat-docs-webapp
tomcat-webapps
tomcat-javadoc
tomcat-el-3_0-api
tomcat-jsp-2_3-api
tomcat10-el-5_0-api
tomcat10-servlet-6_0-api
tomcat10-webapps
tomcat10-lib
tomcat10-jsp-3_1-api
tomcat10-admin-webapps
tomcat10
tomcat11-lib
tomcat11-admin-webapps
tomcat11-servlet-6_1-api
tomcat11-el-6_0-api
tomcat11-webapps
tomcat11-jsp-4_0-api
tomcat11
tomcat11-embed
tomcat11-jsvc
tomcat11-docs-webapp
tomcat11-doc

How to mitigate CVE-2026-66299

Install security update from vendor's website.

Apache Tomcat - addressed in versions 9.0.121, 10.1.59, 11.0.25
tomcat-help - update to 9.0.120-2
tomcat-jsvc - update to 9.0.120-2
tomcat - update to 9.0.120-2
tomcat-servlet-4_0-api - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat-lib - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat-admin-webapps - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat-docs-webapp - update to 9.0.121-3.177.3
tomcat-webapps - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat-javadoc - update to 9.0.121-3.177.3
tomcat-el-3_0-api - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat-jsp-2_3-api - addressed in versions 9.0.121-3.177.3, 9.0.121-150200.120.1
tomcat10-el-5_0-api - update to 10.1.59-150200.5.79.1
tomcat10-servlet-6_0-api - update to 10.1.59-150200.5.79.1
tomcat10-webapps - update to 10.1.59-150200.5.79.1
tomcat10-lib - update to 10.1.59-150200.5.79.1
tomcat10-jsp-3_1-api - update to 10.1.59-150200.5.79.1
tomcat10-admin-webapps - update to 10.1.59-150200.5.79.1
tomcat10 - update to 10.1.59-150200.5.79.1
tomcat11-lib - update to 11.0.25-150600.13.33.2
tomcat11-admin-webapps - update to 11.0.25-150600.13.33.2
tomcat11-servlet-6_1-api - update to 11.0.25-150600.13.33.2
tomcat11-el-6_0-api - update to 11.0.25-150600.13.33.2
tomcat11-webapps - update to 11.0.25-150600.13.33.2
tomcat11-jsp-4_0-api - update to 11.0.25-150600.13.33.2
tomcat11 - update to 11.0.25-150600.13.33.2
tomcat11-embed - update to 11.0.25-150600.13.33.2
tomcat11-jsvc - update to 11.0.25-150600.13.33.2
tomcat11-docs-webapp - update to 11.0.25-150600.13.33.2
tomcat11-doc - update to 11.0.25-150600.13.33.2

External References

Related Security Bulletins