<!-- # Exploit Title: Sagemcom router insecure deserialization > privilege escalation # Date: 08-31-2020 # Exploit Author: Ryan Delaney # Author Contact: ryan.delaney () owasp org # Author LinkedIn: https://www.linkedin.com/in/infosecrd/ # Vendor Homepage: https://sagemcom.com/en # Software Link: N/A (F@ST 5280 firmware not published) # Version: F@ST 5280 router, F/W 1.150.61, possibly others # Tested on: F@ST 5280 router, F/W 1.150.61 # CVE: CVE-2020-24034
1. Description Sagemcom F@ST 5280 routers using firmware version 1.150.61, and possibly others, have an insecure deserialization vulnerability that allows any authenticated user to perform a privilege escalation to any other user. By making a request with valid sess_id, nonce, and ha1 values inside of the serialized session cookie, an attacker may alter the user value inside of this cookie, and assume the role and permissions of the user specified. By assuming the role of the user 'internal', which is inaccessible to end users by default, the attacker gains the permissions of the 'internal' account, which includes the ability to flash custom firmware to the router, allowing the attacker to achieve a complete compromise. Note that the 'internal' account is disabled and hidden by default, and the primary administrative account ('admin'), lacks the permission to flash custom firmware to the device, meaning that an attacker exploiting this vulnerability obtains access exceeding that of the legitimate, authorized system administrator. 2. Proof of Concept Log in as a valid user (default is admin:admin). Retrieve the 'session' cookie. Simply change the only occurrence of the string "admin" within the cookie to "internal", and make a new request with this modified cookie. If you decode the cookie, you will note this is the 4th key value pair inside of the cookie, where the key is "user", and the value is "admin". 3. Solution This vulnerability is only exploitable with a valid existing session. Changing the administrative password to a strong, non-default value, and ensuring that TLS certificate has the correct fingerprint will help prevent attackers from obtaining a valid existing session. --> _______________________________________________ Sent through the Full Disclosure mailing list https://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/