CVE-1999-0208

Step 1: Target Identification: The attacker identifies systems running the vulnerable rpc.ypupdated service, typically by port scanning (port 111 for RPC, and potentially other ports for NIS-related services).

Step 2: Payload Crafting: The attacker crafts a malicious RPC request. This request is specifically designed to exploit the vulnerability in rpc.ypupdated. The request includes a command to be executed on the target system.

Step 3: Request Delivery: The attacker sends the crafted RPC request to the target system's rpc.ypupdated service.

Step 4: Command Execution: The rpc.ypupdated service, lacking proper input validation, processes the malicious request. The embedded command is executed with the privileges of the rpc.ypupdated service, often root.

Step 5: System Compromise: The executed command allows the attacker to gain control of the system. This can include creating backdoors, installing malware, stealing data, and escalating privileges.

The vulnerability lies within the rpc.ypupdated service, specifically in its handling of updates to the NIS database. The service, designed to update NIS maps, lacks proper input validation and authorization checks. Attackers can craft malicious RPC requests containing arbitrary commands. When the service processes these requests, it executes the supplied commands with elevated privileges, typically root, leading to complete system compromise. The root cause is a failure to sanitize user-supplied input before passing it to a system call, resulting in command injection.