CVE-2021-28169
MEDIUMCVE-2021-28169 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in org.eclipse.jetty:jetty-servlets. O3 Security confirms whether CVE-2021-28169 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Jetty Utility Servlets ConcatServlet Double Decoding Information Disclosure Vulnerability
Blast Radius
org.eclipse.jetty:jetty-servlets☕org.eclipse.jetty:jetty-servlets☕org.eclipse.jetty:jetty-servletsReal-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
For Eclipse Jetty versions <= 9.4.40, <= 10.0.2, <= 11.0.2, it is possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory. For example a request to /concat?/%2557EB-INF/web.xml can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.eclipse.jetty:jetty-servlets | all versions | 9.4.41 |
| ☕Maven | org.eclipse.jetty:jetty-servlets | ≥ 10.0.0&&< 10.0.3 | 10.0.3 |
| ☕Maven | org.eclipse.jetty:jetty-servlets | ≥ 11.0.0&&< 11.0.3 | 11.0.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.jetty:jetty-servlets. 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.eclipse.jetty:jetty-servlets to 9.4.41 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28169 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-2021-28169 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-2021-28169. 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-2021-28169 in your dependencies?
O3 detects CVE-2021-28169 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.