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.

From the reporter

XmlParser is vulnerable to XML external entity (XXE) vulnerability. XmlParser is being used when parsing Jetty’s xml configuration files. An attacker might exploit this vulnerability in order to achieve SSRF or cause a denial of service. One possible scenario is importing a (remote) malicious WAR into a Jetty’s server, while the WAR includes a malicious web.xml.

Impact

There are no circumstances in a normally deployed Jetty server where potentially hostile XML is given to the XmlParser class without the attacker already having arbitrary access to the server. I.e. in order to exploit XmlParser the attacker would already have the ability to deploy and execute hostile code. Specifically, Jetty has no protection against malicious web application and potentially hostile web applications should only be run on an isolated virtualisation.

Thus this is not considered a vulnerability of the Jetty server itself, as any such usage of the jetty XmlParser is equally vulnerable as a direct usage of the JVM supplied SAX parser. No CVE will be allocated to this advisory.

However, any direct usage of the XmlParser class by an application may be vulnerable. The impact would greatly depend on how the application uses XmlParser, but it could be a denial of service due to large entity expansion, or possibly the revealing local files if the XML results are accessible remotely.

Patches

Ability to configure the SAXParserFactory to fit the needs of your particular XML parser implementation have been merged as part of PR #10067

Workarounds

Don't use Jetty's XmlParser to parse data from users.

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 and/or the WelcomeFilter by using the code from the latest version of Jetty.

Jetty is a 100% Java HTTP Server and Servlet Container. This means that you do not need to configure and run a separate web server (like Apache) in order\ to use Java, servlets and JSPs to generate dynamic content. Jetty is a fully\ featured web server for static and dynamic content. Unlike separate\ server/container solutions, this means that your web server and web\ application run in the same process, without interconnection overheads\ and complications. Furthermore, as a pure java component, Jetty can be simply\ included in your application for demonstration, distribution or deployment.\ Jetty is available on all Java supported platforms. \ %global extdesc \ \ This package contains

Security Fix(es):

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.(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.

TuxCare rebuilt 4 packages to address 7 CVEs. Fixed in 9.4.48.v20220622-tuxcare.1.

TuxCare rebuilt 7 packages to address 14 CVEs. Fixed in 9.4.50.v20221201-tuxcare.1.

TuxCare rebuilt 4 org.eclipse.jetty packages to address 12 CVEs. Fixed in 9.2.16.v20160414-tuxcare.1.

This update for jetty-minimal fixes the following issues:

Update to version 9.4.42.v20210604

• Fix: bsc#1187117, CVE-2021-28169 - possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory
• Fix: bsc#1184367, CVE-2021-28165 - jetty server high CPU when client send data length > 17408
• Fix: bsc#1184368, CVE-2021-28164 - Normalize ambiguous URIs
• Fix: bsc#1184366, CVE-2021-28163 - Exclude webapps directory from deployment scan

These are all security issues fixed in the jetty-annotations-9.4.43-1.2 package on the GA media of openSUSE Tumbleweed.

This update for jetty-minimal fixes the following issues:

Update to version 9.4.42.v20210604

• Fix: bsc#1187117, CVE-2021-28169 - possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory
• Fix: bsc#1184367, CVE-2021-28165 - jetty server high CPU when client send data length > 17408
• Fix: bsc#1184368, CVE-2021-28164 - Normalize ambiguous URIs
• Fix: bsc#1184366, CVE-2021-28163 - Exclude webapps directory from deployment scan