Sharepoint Dynamic Proxy Generator Remote Command Execution
Posted on 27 March 2024
This Metasploit module exploits two vulnerabilities in Sharepoint 2019 - an authentication bypass as noted in CVE-2023-29357 which was patched in June of 2023 and CVE-2023-24955 which was a remote command execution vulnerability patched in May of 2023. The authentication bypass allows attackers to impersonate the Sharepoint Admin user. This vulnerability stems from the signature validation check used to verify JSON Web Tokens (JWTs) used for OAuth authentication. If the signing algorithm of the user-provided JWT is set to none, SharePoint skips the signature validation step due to a logic flaw in the ReadTokenCore() method. After impersonating the administrator user, the attacker has access to the Sharepoint API and is able to exploit CVE-2023-24955. This authenticated remote command execution vulnerability leverages the impersonated privileged account to replace the /BusinessDataMetadataCatalog/BDCMetadata.bdcm file in the webroot directory with a payload. The payload is then compiled and executed by Sharepoint allowing attackers to remotely execute commands via the API.
