Answer in brief
CVE-2021-28169 records a Medium severity (CVSS 5.3) vulnerability in Jetty Utility Servlets ConcatServlet Double Decoding Information Disclosure Vulnerability. The current sources do not mark it as known exploited. The current feed maps org.eclipse.jetty:jetty-servlets (maven), org.eclipse.jetty:jetty-servlets (maven), org.eclipse.jetty:jetty-servlets (maven). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps org.eclipse.jetty:jetty-servlets (maven), org.eclipse.jetty:jetty-servlets (maven), org.eclipse.jetty:jetty-servlets (maven). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| org.eclipse.jetty:jetty-servletsmaven | >=0 <9.4.41 | 9.4.41 |
| org.eclipse.jetty:jetty-servletsmaven | >=10.0.0 <10.0.3 | 10.0.3 |
| org.eclipse.jetty:jetty-servletsmaven | >=11.0.0 <11.0.3 | 11.0.3 |
Published upstream
Jun 10, 2021
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Sep 10, 2026
Requests to the `ConcatServlet` and `WelcomeFilter` are able to access protected resources within the `WEB-INF` directory. For example a request to the `ConcatServlet` with a URI of `/concat?/%2557EB-INF/web.xml` can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application. This occurs because both `ConcatServlet` and `WelcomeFilter` decode the supplied path to verify it is not within the `WEB-INF` or `META-INF` directories. It then uses this decoded path to call `RequestDispatcher` which will also do decoding of the path. This double decoding allows paths with a doubly encoded `WEB-INF` to bypass this security check. ### Impact This affects all versions of `ConcatServlet` and `WelcomeFilter` in versions before 9.4.41, 10.0.3 and 11.0.3. ### Workarounds If you cannot update to the latest version of Jetty, you can instead deploy your own version of the [`ConcatServlet`](https://github.com/eclipse/jetty.project/blob/4204526d2fdad355e233f6bf18a44bfe028ee00b/jetty-servlets/src/main/java/org/eclipse/jetty/servlets/ConcatServlet.java) and/or the [`WelcomeFilter`](https://github.com/eclipse/jetty.project/blob/4204526d2fdad355e233f6bf18a44bfe028ee00b/jetty-servlets/src/main/java/org/eclipse/jetty/servlets/WelcomeFilter.java) by using the code from the latest version of Jetty.
Quoted source text, attributed separately from HOL analysis.