Server-Side Forgery Request can be activated unmarshalling with XStream
ImpactThe vulnerability may allow a remote attacker to request data from internal resources that are not publicly available only by manipulating the processed input stream.PatchesIf you rely on XStream's default blacklist of the [Security Framework](https://x-stream.github.io/security.html#framework), you will have to use at least version 1.4.15.WorkaroundsThe reported vulnerability does not exist running Java 15 or higher.No user is affected, who followed the recommendation to setup XStream's Security Framework with a whitelist! Anyone relying on XStream's default blacklist can immediately switch to a whilelist for the allowed types to avoid the vulnerability.Users of XStream 1.4.14 or below who still insist to use XStream default blacklist - despite that clear recommendation - can use a workaround depending on their version in use.Users of XStream 1.4.14 can simply add two lines to XStream's setup code:Users of XStream 1.4.14 to 1.4.13 can simply add three lines to XStream's setup code:Users of XStream 1.4.12 to 1.4.7 who want to use XStream with a black list will have to setup such a list from scratch and deny at least the following types: _javax.imageio.ImageIO$ContainsFilter_, _java.beans.EventHandler_, _java.lang.ProcessBuilder_, _jdk.nashorn.internal.objects.NativeString.class_, _java.lang.Void_ and _void_ and deny several types by name pattern.Users of XStream 1.4.6 or below can register an own converter to prevent the unmarshalling of the currently know critical types of the Java runtime. It is in fact an updated version of the workaround for CVE-2013-7285:For more informationIf you have any questions or comments about this advisory:Open an issue in [XStream](https://github.com/x-stream/xstream/issues)Contact us at [XStream Google Group](https://groups.google.com/group/xstream-user)