CVE-2025-53506
HIGHApache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 11.0.0-M1&&< 11.0.9 | 11.0.9 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 10.1.0-M1&&< 10.1.43 | 10.1.43 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 9.0.0.M1&&< 9.0.107 | 9.0.107 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 8.5.0 | No fix |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 8.5.0 | No fix |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 9.0.0.M1&&< 9.0.107 | 9.0.107 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat-coyote. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.apache.tomcat:tomcat-coyote to 11.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-53506 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-53506 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-53506. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-53506 in your dependencies?
O3 detects CVE-2025-53506 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.