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Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams

High severity GitHub Reviewed Published Jul 10, 2025 to the GitHub Advisory Database • Updated Mar 6, 2026

Package

maven org.apache.tomcat.embed:tomcat-embed-core (Maven)

Affected versions

>= 8.5.0, <= 8.5.100
>= 9.0.0.M1, < 9.0.107
>= 10.1.0-M1, < 10.1.43
>= 11.0.0-M1, < 11.0.9

Patched versions

9.0.107
10.1.43
11.0.9
maven org.apache.tomcat:tomcat-coyote (Maven)
>= 11.0.0-M1, < 11.0.9
>= 10.1.0-M1, < 10.1.43
>= 9.0.0.M1, < 9.0.107
>= 8.5.0, <= 8.5.100
11.0.9
10.1.43
9.0.107

Description

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.

Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.

References

Published by the National Vulnerability Database Jul 10, 2025
Published to the GitHub Advisory Database Jul 10, 2025
Reviewed Jul 11, 2025
Last updated Mar 6, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(47th percentile)

Weaknesses

Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource. Learn more on MITRE.

CVE ID

CVE-2025-53506

GHSA ID

GHSA-25xr-qj8w-c4vf

Source code

Credits

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