Apache Tomcat 9.0.x/10.x/11.x WebSocket Close DoS (Uncontrolled Resource)
CVE-2026-77791 Published on September 23, 2026

Apache Tomcat: DoS via busy wait during WebSocket close
Uncontrolled Resource Consumption vulnerability in Apache Tomcat during sending of WebSocket close message enabled a DoS attack. This issue affects Apache Tomcat: from 11.0.0-M5 through 11.0.25, from 10.1.8 through 10.1.59, from 9.0.74 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.88 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-77791 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Exploitation:
NONE
Automatable:
YES
Technical Impact:
PARTIAL
Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Weakness Type

What is a Resource Exhaustion Vulnerability?

The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.

CVE-2026-77791 has been classified to as a Resource Exhaustion vulnerability or weakness.


Products Associated with CVE-2026-77791

stack.watch emails you whenever new vulnerabilities are published in Apache Tomcat or Oracle. Just hit a watch button to start following.

Apache Tomcat
Oracle

Affected Versions

Apache Software Foundation Apache Tomcat:

Exploit Probability

EPSS
0.68%
Percentile
52.91%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.