CVE-2025-64129: Zenitel TCIV-3+ DoS Vulnerability

CVE-2025-64129 Overview

Zenitel TCIV-3+ is vulnerable to an out-of-bounds write vulnerability (CWE-787), which could allow a remote attacker to crash the device. This memory corruption flaw affects the Zenitel TCIV-3+ intercom device and represents a significant security risk for organizations deploying these devices in critical infrastructure environments.

Critical Impact

Remote attackers can exploit this out-of-bounds write vulnerability to crash Zenitel TCIV-3+ devices, potentially disrupting communication capabilities in security-critical environments where these intercom systems are deployed.

Affected Products

• Zenitel TCIV-3+ Intercom Device
• Zenitel Station and Device Firmware (versions prior to patched release)

Discovery Timeline

• 2025-11-26 - CVE-2025-64129 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-64129

Vulnerability Analysis

This vulnerability is classified as an out-of-bounds write (CWE-787), a type of memory corruption flaw where the application writes data past the boundaries of allocated memory buffers. In the context of the Zenitel TCIV-3+ device, this vulnerability can be triggered remotely over the network, requiring user interaction to exploit successfully.

The vulnerability impacts device availability significantly, allowing attackers to cause denial of service conditions by crashing the affected intercom system. Additionally, there is potential for limited confidentiality and integrity impacts on the device.

Root Cause

The root cause of this vulnerability lies in improper bounds checking when handling input data. Out-of-bounds write vulnerabilities typically occur when an application fails to properly validate the size or index of data being written to a memory buffer. In embedded devices like the TCIV-3+, such flaws can result from insufficient input validation in network-facing services or protocol handlers.

Attack Vector

The attack vector is network-based, meaning attackers can exploit this vulnerability remotely without requiring prior authentication. However, successful exploitation requires some form of user interaction. An attacker could craft malicious network packets or requests designed to trigger the out-of-bounds write condition, ultimately causing the device to crash and become unavailable.

The vulnerability does not currently have known public exploits available, and it is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.

Detection Methods for CVE-2025-64129

Indicators of Compromise

• Unexpected device crashes or reboots of Zenitel TCIV-3+ intercom units
• Unusual network traffic patterns targeting TCIV-3+ devices
• Memory corruption errors in device logs prior to system failures
• Repeated connection attempts from suspicious IP addresses to intercom endpoints

Detection Strategies

• Monitor network traffic for anomalous packets targeting Zenitel TCIV-3+ devices
• Implement intrusion detection rules to identify potential exploitation attempts against intercom systems
• Configure logging on network firewalls to capture traffic destined for TCIV-3+ device ports
• Deploy SentinelOne Singularity for IoT/OT to detect anomalous behavior on embedded devices

Monitoring Recommendations

• Enable comprehensive logging on Zenitel TCIV-3+ devices and forward logs to a centralized SIEM
• Establish baseline network behavior for intercom devices and alert on deviations
• Monitor device availability and set up automated alerts for unexpected reboots or unresponsive states
• Review CISA ICS advisories regularly for updated threat intelligence on this vulnerability

How to Mitigate CVE-2025-64129

Immediate Actions Required

• Review the CISA ICS Advisory #25-329-03 for official guidance
• Identify all Zenitel TCIV-3+ devices in your environment and document their firmware versions
• Restrict network access to TCIV-3+ devices using firewall rules and network segmentation
• Disable remote access to intercom devices where possible until patches are applied

Patch Information

Zenitel has made updated firmware available to address this vulnerability. Organizations should download the latest firmware package from the Zenitel Firmware Package Download page and apply it to all affected TCIV-3+ devices following the vendor's upgrade procedures.

For additional technical details on the vulnerability, refer to the GitHub CSAF Document.

Workarounds

• Implement network segmentation to isolate TCIV-3+ devices from untrusted networks
• Deploy firewalls or access control lists to restrict which systems can communicate with intercom devices
• Disable unnecessary network services on the TCIV-3+ devices if supported
• Monitor and limit user interactions with the device's network interfaces until patching is complete

# Example network segmentation using iptables (Linux firewall host)
# Restrict access to Zenitel TCIV-3+ device to management VLAN only
iptables -A INPUT -s 10.10.10.0/24 -d 192.168.1.100 -j ACCEPT
iptables -A INPUT -d 192.168.1.100 -j DROP