The kernel in Cisco Native Unix (CNU) on Cisco Unified IP Phone 7900 series devices (aka TNP phones) with software before 9.3.1-ES10 does not properly validate unspecified system calls, which allows attackers to execute arbitrary code or cause a denial of service (memory overwrite) via a crafted binary.
Cisco Unified IP Phone 7900 series devices are vulnerable to a critical remote code execution (RCE) vulnerability. Attackers can exploit an unvalidated system call flaw to execute arbitrary code or cause a denial-of-service (DoS) condition, potentially leading to complete system compromise and data exfiltration.
Step 1: Payload Delivery: The attacker crafts a malicious binary specifically designed to exploit the unvalidated system call vulnerability. This binary contains a payload designed to overwrite memory or execute arbitrary code. Step 2: Binary Upload: The attacker uploads the malicious binary to the vulnerable Cisco IP Phone. The method of upload is not specified in the CVE, but could involve network access or physical access. Step 3: System Call Trigger: The attacker triggers the vulnerable system call, likely by executing the uploaded binary or by causing the phone to execute it. Step 4: Memory Corruption: The crafted input to the system call causes a memory overwrite, potentially leading to a buffer overflow or other memory corruption. This overwrite can corrupt critical kernel data structures. Step 5: Code Execution/DoS: Depending on the payload, the attacker can achieve arbitrary code execution within the kernel context, or cause a denial-of-service (DoS) by crashing the phone or rendering it unusable.
The vulnerability stems from insufficient input validation within the Cisco Native Unix (CNU) kernel of the affected IP phones. Specifically, the kernel fails to properly validate arguments passed to certain system calls. This lack of validation allows a crafted binary, designed to exploit the vulnerability, to overwrite memory. The root cause is a buffer overflow or similar memory corruption issue triggered by a system call with malformed or oversized input. The specific function or logic flaw is not explicitly stated in the CVE description, but the impact is clear: the attacker can control the execution flow of the phone's kernel.