This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of QNAP QTS. Authentication is not required to exploit this vulnerability.
The specific flaw exists within the handling of the OLD_PASSWORD parameter provided to the change_password.cgi endpoint. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code under the context of root.