CVE-2021-25122
HIGHCVE-2021-25122 is a high-severity (CVSS 7.5) Information Exposure vulnerability in org.apache.tomcat.embed:tomcat-embed-core. O3 Security confirms whether CVE-2021-25122 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Exposure of Sensitive Information to an Unauthorized Actor 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-coyoteReal-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
When responding to new h2c connection requests, Apache Tomcat versions 10.0.0-M1 to 10.0.0, 9.0.0.M1 to 9.0.41 and 8.5.0 to 8.5.61 could duplicate request headers and a limited amount of request body from one request to another meaning user A and user B could both see the results of user A's request.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 10.0.0-M1&&< 10.0.2 | 10.0.2 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 9.0.0-M1&&< 9.0.43 | 9.0.43 |
| ☕Maven | org.apache.tomcat.embed:tomcat-embed-core | ≥ 8.5.0&&< 8.5.63 | 8.5.63 |
| ☕Maven | org.apache.tomcat:tomcat-coyote | ≥ 10.0.0-M1&&< 10.0.2 | 10.0.2 |
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 10.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25122 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-2021-25122 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-2021-25122. 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.
Red Hat Enterprise Linux 8's Identity Management and Certificate System are using a vulnerable version of Tomcat that is bundled into the `pki-servlet-engine` component. However, HTTP/2 is not enabled in such a configuration, and it is not possible to trigger the flaw in a supported setup. A future update may fix the…
Frequently Asked Questions
Is CVE-2021-25122 in your dependencies?
O3 detects CVE-2021-25122 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.