CVE-2025-64128: OS Command Injection RCE Vulnerability

CVE-2025-64128 Overview

An OS command injection vulnerability exists in Zenitel devices due to incomplete validation of user-supplied input. The validation mechanism fails to enforce sufficient formatting rules, which permits attackers to append arbitrary data to system commands. This critical flaw allows an unauthenticated attacker to inject and execute arbitrary commands on the underlying operating system, potentially leading to complete system compromise.

Critical Impact

This vulnerability enables unauthenticated remote attackers to execute arbitrary OS commands with no user interaction required, potentially resulting in full device takeover and lateral movement within ICS/OT environments.

Affected Products

• Zenitel Station and Device Firmware (VS-IS)
• Zenitel Intercom Devices
• Zenitel ICS/OT Communication Equipment

Discovery Timeline

• 2025-11-26 - CVE-2025-64128 published to NVD
• 2025-12-01 - Last updated in NVD database

Technical Details for CVE-2025-64128

Vulnerability Analysis

This vulnerability is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The flaw originates from the application's failure to properly sanitize user-controlled input before incorporating it into system-level command execution.

The incomplete input validation allows attackers to bypass security controls by injecting shell metacharacters or command separators that the application does not properly filter. When the malformed input is processed, the injected commands are executed with the privileges of the application process, typically running with elevated permissions on embedded devices.

Given the network-accessible nature of this vulnerability and the fact that no authentication is required, attackers can remotely exploit this flaw without any prior access to the system. The attack complexity is low, making exploitation straightforward for threat actors with basic knowledge of command injection techniques.

Root Cause

The root cause lies in the insufficient input validation routines that fail to enforce proper formatting rules on user-supplied data. The application does not adequately sanitize special characters such as semicolons (;), pipes (|), backticks (`), or shell command substitution sequences ($()) before passing input to system command execution functions. This allows attackers to break out of the intended command context and append arbitrary commands.

Attack Vector

The attack can be executed remotely over the network without authentication. An attacker would identify input fields or API endpoints that accept user data and ultimately pass it to OS command execution. By crafting malicious input containing command injection payloads, the attacker can execute arbitrary commands on the target system.

The exploitation mechanism involves appending command separators followed by malicious commands to legitimate input values. When the application constructs and executes the system command, the injected payload is interpreted by the shell and executed alongside or instead of the intended operation.

For technical details on the vulnerability and exploitation vectors, refer to the CISA ICS Advisory.

Detection Methods for CVE-2025-64128

Indicators of Compromise

• Unusual outbound network connections from Zenitel devices to unknown external IP addresses
• Unexpected process spawning or shell execution on affected devices
• Anomalous system commands in device logs containing shell metacharacters
• Evidence of data exfiltration or unauthorized configuration changes on intercom systems

Detection Strategies

• Monitor network traffic for suspicious HTTP/HTTPS requests containing command injection patterns such as encoded semicolons, pipes, or backticks
• Implement IDS/IPS rules to detect common OS command injection payloads targeting Zenitel devices
• Deploy behavioral analysis to identify abnormal process execution chains on embedded devices
• Review application and system logs for error messages indicating command parsing failures or unexpected shell invocations

Monitoring Recommendations

• Enable comprehensive logging on all Zenitel devices and forward logs to a centralized SIEM
• Configure alerts for any authentication failures followed by successful command execution
• Monitor for changes to critical system files or configuration on affected devices
• Establish baseline behavior patterns for network communication and process activity to detect deviations

How to Mitigate CVE-2025-64128

Immediate Actions Required

• Isolate affected Zenitel devices from direct internet exposure using network segmentation
• Implement strict firewall rules to limit access to affected devices to trusted IP addresses only
• Review and audit all network-accessible interfaces on Zenitel equipment
• Enable enhanced logging and monitoring on affected systems pending patch deployment

Patch Information

Zenitel has released updated firmware to address this vulnerability. Organizations should download and apply the latest Station and Device Firmware Package (VS-IS) from the Zenitel Firmware Package Download page. Before deploying the patch in production environments, test the update in a controlled setting to ensure compatibility with existing configurations.

For additional guidance and technical details, consult the CISA ICS Advisory and the GitHub CSAF File.

Workarounds

• Deploy a Web Application Firewall (WAF) or API gateway to filter malicious input containing command injection patterns
• Restrict network access to affected devices using VPN or jump host architectures
• Disable unnecessary network services and interfaces on Zenitel devices to reduce attack surface
• Implement network-level monitoring to detect and block exploitation attempts in real-time

# Example network isolation configuration (firewall rules)
# Restrict access to Zenitel devices to management network only
iptables -A INPUT -s 10.0.0.0/24 -d <ZENITEL_DEVICE_IP> -j ACCEPT
iptables -A INPUT -d <ZENITEL_DEVICE_IP> -j DROP