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
openEuler
tomcat
tomcat-help
tomcat-jsvc
openEuler
tomcat
tomcat-help
tomcat-jsvc
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 - update to 9.0.120-2
tomcat-help - update to 9.0.120-2
tomcat-jsvc - update to 9.0.120-2
tomcat - update to 9.0.120-2
tomcat-help - update to 9.0.120-2
tomcat-jsvc - update to 9.0.120-2
External References
- https://tomcat.apache.org/security-11.html#Fixed_in_Apache_Tomcat_11.0.25
- https://github.com/apache/tomcat/commit/4e8e3f8964e9653bab427bf794e026c69ee80f2b
- https://tomcat.apache.org/security-10.html#Fixed_in_Apache_Tomcat_10.1.58
- https://tomcat.apache.org/security-9.html#Fixed_in_Apache_Tomcat_9.0.121
- https://tomcat.apache.org/security-10.html#Fixed_in_Apache_Tomcat_10.1.59