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. 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: 0.00198 epss-percentile: 0.57535 cpe: cpe:2.3:a:redhat:keycloak:*:*:*:*:*:*:*:* metadata: verified: true max-request: 4 vendor: redhat product: keycloak shodan-query: html:"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\":1}" stop-at-first-match: true headers: Content-Type: application/json matchers-condition: and matchers: - type: word part: body words: - 'Unrecognized field "Test' - type: word part: header words: - text/html - type: status status: - 400 # digest: 4a0a00473045022100e25e2f7fb7bb3abd466594514ccad68062d38419c57c3213ff79a3ac2f59cc7b02200da4e30bff802060e76527ce98ba4c84fbc72a20c441d06c9361aa8ca395fe1e:922c64590222798bb761d5b6d8e72950