Impact With Jetty 12+ a user can craft a URL to access any resource the Jetty instance is allowed to access. For example "http://[host]/xwiki/bin/skin/..%252f/..%252f..%252f..%252f..%252f..%252f..%252f..%252fetc/passwd" allows downloading the content of the /etc/passwd file, provided Jetty is allowed to read it, and if your XWiki webapp is located exactly 5 levels below "/" (like "/var/lib/jetty/webapps/xwiki", which is the case in the docker image, for example). Another example which does not go out of the XWiki webapp, but it's still a vulnerability (since users should not be allowed to access Hibernate or XWiki configuration files) is "http://[host]/xwiki/bin/skin/..%252f/..%252fWEB-INF/xwiki.cfg". Patches This vulnerability has been patched in XWiki 17.10.5 and 18.2.0. Workarounds A possible workaround is to use a different application server, like Jetty < 12 (in the case of XWiki < 17) or Tomcat, which don't seem to be impacted. Resources * https://jira.xwiki.org/browse/XWIKI-24075 * https://jira.xwiki.org/browse/XCOMMONS-3594 For more information If there are any questions or comments about this advisory: * Open an issue in "Jira XWiki.org" (https://jira.xwiki.org/) * Send an email to the "Security Mailing List" (mailto:security@xwiki.org) Attribution Lê Ngọc Khoa reported the vulnerability.