CVE-2020-13935
HIGHInfinite Loop in Apache Tomcat
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☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat.embed:tomcat-embed-websocket☕org.apache.tomcat.embed:tomcat-embed-websocket☕org.apache.tomcat.embed:tomcat-embed-websocket☕org.apache.tomcat.embed:tomcat-embed-websocket+4 moreReal-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
The payload length in a WebSocket frame was not correctly validated in Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M1 to 9.0.36, 8.5.0 to 8.5.56 and 7.0.27 to 7.0.104. Invalid payload lengths could trigger an infinite loop. Multiple requests with invalid payload lengths could lead to a denial of service.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.0.0-M1&&< 10.0.0-M7 | 10.0.0-M7 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 9.0.0.M1&&< 9.0.37 | 9.0.37 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 8.5.0&&< 8.5.57 | 8.5.57 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 7.0.27&&< 7.0.105 | 7.0.105 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-websocket | ≥ 7.0.27&&< 7.0.105 | 7.0.105 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-websocket | ≥ 8.5.0&&< 8.5.57 | 8.5.57 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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. 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 to 10.0.0-M7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-13935 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-2020-13935 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-2020-13935. 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-2020-13935 in your dependencies?
O3 detects CVE-2020-13935 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.