CVE-2025-53506: tomcat DoS — Fix

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

Affected Products

Vendor	Product	Versions
apache	tomcat	9.0.0 — 9.0.106
apache	tomcat	10.1.0 — 10.1.42
apache	tomcat	11.0.0 — 11.0.8

References

Advisories & Patches

https://lists.apache.org/thread/p09775q0rd185m6zz98krg0fp45j8kr0

Other References

http://www.openwall.com/lists/oss-security/2025/07/10/13 https://lists.debian.org/debian-lts-announce/2025/07/msg00009.html

Frequently Asked Questions

What is CVE-2025-53506? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-53506? +

CVE-2025-53506 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-53506? +

CVE-2025-53506 affects products from apache, specifically: tomcat. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-53506? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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