Apache Tomcat <9.0.107 HTTP/2 Uncontrolled Resource Consumption
CVE-2025-53506 Published on July 10, 2025
Apache Tomcat: DoS via excessive h2 streams at connection start
Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106.
The following versions were EOL at the time the CVE was created but are
known to be affected: 8.5.0 through 8.5.100. Other EOL versions may also be affected.
Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.
Vulnerability Analysis
CVE-2025-53506 is exploitable 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.
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-2025-53506 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2025-53506
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Affected Versions
Apache Software Foundation Apache Tomcat:- Version 11.0.0-M1, <= 11.0.8 is affected.
- Version 10.1.0-M1, <= 10.1.42 is affected.
- Version 9.0.0.M1, <= 9.0.106 is affected.
- Version 8.5.0, <= 8.5.100 is affected.
- Version 10.0.0-M1, <= 10.0.27 is unknown.
Exploit Probability
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.