CVE-2020-26258

XStream is a Java library to serialize objects to XML and back again. In XStream before version 1.4.15, a Server-Side Forgery Request vulnerability can be activated when unmarshalling. The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available only by manipulating the processed input stream. If you rely on XStream's default blacklist of the Security Framework, you will have to use at least version 1.4.15. The reported vulnerability does not exist if 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 want to use XStream default blacklist can use a workaround described in more detailed in the referenced advisories.

### Impact The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available only by manipulating the processed input stream. ### Patches If 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. ### Workarounds The 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: ```Java xstream.denyTypes(new String[]{ "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` Users of XStream 1.4.14 to 1.4.13 can simply add three lines to XStream's setup code: ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` 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$ContainsFilter_, _java.beans.EventHandler_, _java.lang.ProcessBuilder_, _jdk.nashorn.internal.objects.NativeString.class_, _java.lang.Void_ and _void_ and deny several types by name pattern. ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class, "jdk.nashorn.internal.objects.NativeString", java.beans.EventHandler.class, java.lang.ProcessBuilder.class, java.lang.Void.class, void.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\$LazyIterator", "javax\\.crypto\\..*", ".*\\.ReadAllStream\\$FileStream" }); ``` 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: ```Java xstream.registerConverter(new Converter() { public boolean canConvert(Class type) { return type != null && (type == java.beans.EventHandler.class || type == java.lang.ProcessBuilder.class || type.getName().equals("javax.imageio.ImageIO$ContainsFilter") || type.getName().equals("jdk.nashorn.internal.objects.NativeString") || type == java.lang.Void.class || void.class || Proxy.isProxy(type)) || type.getName().startsWith("javax.crypto.") || type.getName().endsWith("$LazyIterator") || type.getName().endsWith(".ReadAllStream$FileStream")); } public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } }, XStream.PRIORITY_LOW); ``` ### For more information If 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)

### Impact The vulnerability may allow a remote attacker to request data from internal resources that are not publicly available only by manipulating the processed input stream. ### Patches If 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. ### Workarounds The 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: ```Java xstream.denyTypes(new String[]{ "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` Users of XStream 1.4.14 to 1.4.13 can simply add three lines to XStream's setup code: ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" }); ``` 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$ContainsFilter_, _java.beans.EventHandler_, _java.lang.ProcessBuilder_, _jdk.nashorn.internal.objects.NativeString.class_, _java.lang.Void_ and _void_ and deny several types by name pattern. ```Java xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" }); xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class, "jdk.nashorn.internal.objects.NativeString", java.beans.EventHandler.class, java.lang.ProcessBuilder.class, java.lang.Void.class, void.class }); xstream.denyTypesByRegExp(new String[]{ ".*\\$LazyIterator", "javax\\.crypto\\..*", ".*\\.ReadAllStream\\$FileStream" }); ``` 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: ```Java xstream.registerConverter(new Converter() { public boolean canConvert(Class type) { return type != null && (type == java.beans.EventHandler.class || type == java.lang.ProcessBuilder.class || type.getName().equals("javax.imageio.ImageIO$ContainsFilter") || type.getName().equals("jdk.nashorn.internal.objects.NativeString") || type == java.lang.Void.class || void.class || Proxy.isProxy(type)) || type.getName().startsWith("javax.crypto.") || type.getName().endsWith("$LazyIterator") || type.getName().endsWith(".ReadAllStream$FileStream")); } public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { throw new ConversionException("Unsupported type due to security reasons."); } }, XStream.PRIORITY_LOW); ``` ### For more information If 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)

XStream es una biblioteca de Java para serializar objetos a XML y viceversa. En XStream versiones anteriores a 1.4.15, puede ser activada una vulnerabilidad de tipo Server-Side Forgery Request al desagrupar. La vulnerabilidad puede permitir a un atacante remoto solicitar datos de recursos internos que no están disponibles públicamente solo mediante la manipulación del flujo de entrada procesado. Si confía en la lista negra predeterminada de XStream del Security Framework, tendrá que usar al menos la versión 1.4.15. La vulnerabilidad reportada no existe si se ejecuta Java versión 15 o superior. Ningún usuario es afectado si siguió la recomendación de configurar el Security Framework de XStream con una lista blanca! Cualquiera que confíe en la lista negra predeterminada de XStream puede cambiar inmediatamente a una lista blanca para los tipos permitidos para evitar la vulnerabilidad. Usuarios de XStream 1.4 o por debajo, quienes aún quieran usar la lista negra predeterminada de XStream pueden usar una solución alternativa que se describe con más detalle en los avisos a los que se hace referencia