CVE-2025-53506

Apache Tomcat: DoS via excessive h2 streams at connection start

Published Jul 10, 2025 CVSS 3.1 · 7.5 High EPSS 2.1% KEV · Not listed
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. 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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4244-1 tomcat9 security update
Debian DSA Debian DSA DSA-6120-1 tomcat10 security update
Debian DSA Debian DSA DSA-6121-1 tomcat11 security update
EUVD EUVD EUVD-2025-21032 Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams
Github GHSA Github GHSA GHSA-25xr-qj8w-c4vf Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams
History
Type Values Removed Values Added
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. 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.
Type Values Removed Values Added
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. Older, 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. 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.
Type Values Removed Values Added
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. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue. 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. Older, 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.
Type Values Removed Values Added
First Time appeared Apache
Apache tomcat
CPEs cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
Vendors & Products Apache
Apache tomcat
Type Values Removed Values Added
Metrics epss

{'score': 0.0004}

epss

{'score': 0.00052}

Type Values Removed Values Added
Metrics epss

{'score': 0.00018}

epss

{'score': 0.0004}

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Metrics epss

{'score': 0.00018}

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

epss

{}

threat_severity

Moderate

Type Values Removed Values Added
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. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.
Title Apache Tomcat: DoS via excessive h2 streams at connection start
Weaknesses CWE-400
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
apache
Published
Updated
Nov 4, 2025, 9:11 PM
Reserved
Jul 1, 2025, 2:22 PM
Status
Modified
Published
Jul 10, 2025, 8:15 PM
Modified
Jun 17, 2026, 9:38 AM
Severity
Moderate
Public date
Jul 10, 2025, 7:14 PM