CVE-2025-53506 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in org.apache.tomcat:tomcat-coyote. A fix is available for org.apache.tomcat:tomcat-coyote — see the affected versions and patch details below.
Apache Tomcat: DoS via excessive h2 streams at connection start
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-53506.
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.
How urgent is this, really
CVE-2025-53506 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 | 11.0.9org.apache.tomcat:tomcat-coyote:11.0.9 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 10.1.0-M1&&< 10.1.43 | 10.1.43org.apache.tomcat:tomcat-coyote:10.1.43 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 9.0.0.M1&&< 9.0.107 | 9.0.107org.apache.tomcat:tomcat-coyote: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 | 9.0.107org.apache.tomcat.embed:tomcat-embed-core: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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-53506 can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 10 | tomcat9-1:9.0.87-5.el10_0.3 | RHSA-2025:14178 |
| Red Hat Enterprise Linux 10 | tomcat-1:10.1.36-1.el10_0.2 | RHSA-2025:14179 |
| Red Hat Enterprise Linux 8 | tomcat-1:9.0.87-1.el8_10.6 | RHSA-2025:14177 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | tomcat-1:9.0.87-1.el8_8.7 | RHSA-2025:14182 |
| Red Hat Enterprise Linux 9 | tomcat-1:9.0.87-3.el9_6.3 | RHSA-2025:14181 |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | tomcat-1:9.0.87-1.el9_2.6 | RHSA-2025:14183 |
| Red Hat Enterprise Linux 9.4 Extended Update Support | tomcat-1:9.0.87-1.el9_4.6 | RHSA-2025:14180 |
| Red Hat JBoss Web Server 5.8.5 | jws5-tomcat | RHSA-2025:11696 |
Frequently Asked Questions
Is CVE-2025-53506 in your dependencies?
O3 Security finds CVE-2025-53506 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.