CVE-2020-1935
MEDIUMCVE-2020-1935 is a medium-severity (CVSS 4.8) CWE-444 vulnerability in org.apache.tomcat.embed:tomcat-embed-core. O3 Security confirms whether CVE-2020-1935 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Potential HTTP request smuggling in Apache Tomcat
Real-World Exposure
org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat.embed:tomcat-embed-core☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcatReal-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
In Apache Tomcat 9.0.0.M1 to 9.0.30, 8.5.0 to 8.5.50 and 7.0.0 to 7.0.99 the HTTP header parsing code used an approach to end-of-line parsing that allowed some invalid HTTP headers to be parsed as valid. This led to a possibility of HTTP Request Smuggling if Tomcat was located behind a reverse proxy that incorrectly handled the invalid Transfer-Encoding header in a particular manner. Such a reverse proxy is considered unlikely.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | all versions | 7.0.100 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 8.0.0&&< 8.5.51 | 8.5.51 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 9.0.0&&< 9.0.31 | 9.0.31 |
| ☕Maven | org.apache.tomcat:tomcat | all versions | 7.0.100 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 8.0.0&&< 8.5.51 | 8.5.51 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 9.0.0&&< 9.0.31 | 9.0.31 |
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.embed:tomcat-embed-core. 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.embed:tomcat-embed-core to 7.0.100 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-1935 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-2020-1935 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-2020-1935. 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.
OpenDaylight in Red Hat OpenStack 10 & 13 was in technical preview status, because of this no fixes will be released for it. In Red Hat Satellite 6, Candlepin is using Tomcat to provide a REST API, and has been found to be vulnerable to the flaw. However, it is currently believed that no useful attacks can be carried…
Frequently Asked Questions
Is CVE-2020-1935 in your dependencies?
O3 detects CVE-2020-1935 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.