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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-53506: 2.13% estimated exploitation activity in the next 30 days; percentile 81.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

10 Jul 2025, 21:31 UTC

Last modified by the source

6 Mar 2026, 21:34 UTC

Source last checked

26 Oct 2026, 16:44 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-25xr-qj8w-c4vf

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-53506

Advisory: Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams
IDs: CVE-2025-53506, GHSA-25xr-qj8w-c4vf
Record: https://patchnext.com/advisories/cve-2025-53506 (revision 1, source checked 26 Oct 2026, 16:44 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: org.apache.tomcat:tomcat-coyote 11.0.9, 10.1.43, 9.0.107; org.apache.tomcat.embed:tomcat-embed-core 11.0.9, 10.1.43, 9.0.107. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.apache.tomcat:tomcat-coyote: affected >= 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; fixed in 11.0.9, 9.0.107, 10.1.43
- Maven org.apache.tomcat.embed:tomcat-embed-core: affected >= 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; fixed in 11.0.9, 9.0.107, 10.1.43

## Suggested inspection (read-only)
- Maven org.apache.tomcat:tomcat-coyote: check the installed version with your package manager.
- Maven org.apache.tomcat.embed:tomcat-embed-core: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.apache.tomcat:tomcat-coyote, org.apache.tomcat.embed:tomcat-embed-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-25xr-qj8w-c4vf (GitHub-reviewed advisory GHSA-25xr-qj8w-c4vf lists affected ranges: Maven org.apache.tomcat:tomcat-coyote >=11.0.0-M1 =10.1.0-M1 =9.0.0.M1 =8.5.0 =8.5.0 =9.0.0.M1 =10.1.0-M1 =11.0.0-M1 <11.0.9)

Commands are suggestions: review each one before running it.