Source: psirt@cisco.com
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 vulnerability allowing for arbitrary code execution and denial-of-service. This flaw stems from improper validation of system calls within the CNU kernel, enabling attackers to craft malicious binaries that can overwrite memory and compromise the device. Successful exploitation could lead to complete device takeover and potential network compromise.
Step 1: Payload Delivery: The attacker crafts a malicious binary specifically designed to exploit the vulnerability.
Step 2: Binary Upload: The attacker uploads the crafted binary to the vulnerable Cisco IP phone, potentially through network access or physical access.
Step 3: System Call Trigger: The attacker executes the malicious binary, which triggers the vulnerable system call.
Step 4: Memory Overwrite: The crafted system call arguments cause a buffer overflow, overwriting critical kernel memory.
Step 5: Code Execution/DoS: Depending on the overwritten data, the attacker can either execute arbitrary code (gaining control of the phone) or cause a denial-of-service (by crashing the phone).
The vulnerability lies within the Cisco Native Unix (CNU) kernel's handling of system calls. The kernel fails to adequately validate the parameters passed to these calls, leading to a memory overwrite condition. Specifically, a crafted binary can provide malformed input to a system call, causing it to write data beyond the allocated buffer. This buffer overflow allows an attacker to overwrite critical kernel data structures, potentially hijacking control flow and executing arbitrary code. The root cause is a lack of bounds checking or input validation on system call arguments, allowing for out-of-bounds memory access. The specific function or logic flaw is not explicitly stated in the CVE description, but the implication is a vulnerability in the handling of system call arguments, likely related to data size or pointer validation.
While no specific APTs or malware families are directly linked to this CVE in the provided information, the nature of the vulnerability makes it attractive to various threat actors. Attackers could use this vulnerability for espionage, lateral movement, or to establish a foothold within a network. The vulnerability is not listed in the CISA KEV at the time of this analysis, but given the potential impact, it is a candidate for inclusion.
Network traffic analysis: Monitor for unusual network connections originating from Cisco IP phones, especially those involving file transfers or attempts to execute binaries.
File integrity monitoring: Monitor for unauthorized modifications to system files on the IP phone.
Log analysis: Review system logs for suspicious activity, such as errors related to system calls or kernel crashes.
Endpoint Detection and Response (EDR) on any connected management systems: Look for signs of compromise on systems that manage the phones.
SIEM alerts based on network traffic patterns and log anomalies.
Upgrade to the latest firmware version (9.3.1-ES10 or later) to patch the vulnerability.
Implement network segmentation to isolate the IP phone network from other critical network segments.
Restrict network access to the IP phones, only allowing necessary traffic.
Monitor network traffic for suspicious activity originating from the IP phones.
Regularly audit and update security configurations on the IP phones.
Disable unused services and features on the IP phones.
Implement strong password policies and multi-factor authentication for device access.