CVE-2021-28169

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.

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.

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.

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.

Para Eclipse Jetty versiones anteriores a 9.4.40 incluyéndola, versiones anteriores a 10.0.2 incluyéndola, versiones anteriores a 11.0.2 incluyéndola, es posible que las peticiónes al ConcatServlet con una ruta doblemente codificada acceder a recursos protegidos dentro del directorio WEB-INF.&#xa0;Por ejemplo, una petición a "/concat?/%2557EB-INF/web.xml" puede recuperar el archivo web.xml.&#xa0;Esto puede revelar información confidencial sobre la implementación de una aplicación web