CVE-2025-64055: Fanvil X210 Firmware Auth Bypass Flaw

CVE-2025-64055 Overview

An authentication bypass vulnerability has been discovered in Fanvil X210 V2 firmware version 2.12.20. This critical security flaw allows unauthenticated attackers on the local network to access administrative functions of the device, including file upload, firmware update, and device reboot capabilities. The vulnerability enables complete compromise of the VoIP phone device through a crafted authentication bypass technique.

Critical Impact

Unauthenticated attackers can gain full administrative control over Fanvil X210 devices, potentially enabling firmware manipulation, configuration theft, and denial of service attacks on VoIP infrastructure.

Affected Products

• Fanvil X210 Firmware version 2.12.20
• Fanvil X210 Hardware V2.0
• Fanvil X210 VoIP Phone devices running vulnerable firmware

Discovery Timeline

• 2025-12-03 - CVE-2025-64055 published to NVD
• 2026-01-09 - Last updated in NVD database

Technical Details for CVE-2025-64055

Vulnerability Analysis

This authentication bypass vulnerability (CWE-287: Improper Authentication) affects the Fanvil X210 VoIP phone's web management interface. The flaw allows network-adjacent attackers to circumvent authentication controls entirely, granting unauthorized access to privileged administrative functions without providing valid credentials.

The vulnerability exposes critical device management capabilities including file upload functionality, firmware update mechanisms, and device reboot controls. An attacker exploiting this flaw could upload malicious firmware, extract sensitive configuration data including SIP credentials, or render the device inoperable through forced reboots or configuration manipulation.

The network-based attack vector combined with no privilege requirements and no user interaction needed makes this vulnerability particularly dangerous in enterprise VoIP deployments where multiple Fanvil devices may be accessible on the same network segment.

Root Cause

The root cause of this vulnerability is improper authentication validation in the Fanvil X210 web management interface. The device fails to properly verify authentication tokens or session credentials before granting access to administrative functions, allowing attackers to craft requests that bypass the authentication mechanism entirely.

Attack Vector

The attack is executed over the network by an unauthenticated attacker with access to the local network segment where the vulnerable Fanvil X210 device resides. The attacker crafts specially designed requests that exploit the authentication bypass flaw to gain access to administrative functions.

The vulnerability is particularly concerning because it requires no authentication, operates with low attack complexity, and can be exploited without any user interaction. Once administrative access is obtained, an attacker can:

• Upload malicious files or backdoored firmware
• Extract device configuration including SIP credentials
• Modify device settings to redirect calls or enable eavesdropping
• Cause denial of service by rebooting or bricking the device

For detailed technical information about the exploitation mechanism, see the GitHub Security Advisory for CVE-2025-64055.

Detection Methods for CVE-2025-64055

Indicators of Compromise

• Unexpected administrative login events or sessions on Fanvil X210 devices without corresponding valid authentication
• Unauthorized firmware updates or file uploads detected in device logs
• Configuration changes to VoIP settings or SIP credentials without authorized administrator activity
• Unusual network traffic patterns to the device's web management interface from unexpected sources

Detection Strategies

• Monitor web server access logs on Fanvil X210 devices for authentication bypass attempts and unauthorized administrative access patterns
• Implement network-based intrusion detection to identify suspicious requests targeting the device management interface
• Deploy file integrity monitoring to detect unauthorized firmware or configuration changes
• Audit network traffic for anomalous HTTP requests to Fanvil device management ports

Monitoring Recommendations

• Enable detailed logging on all Fanvil X210 devices and forward logs to a centralized SIEM for analysis
• Implement network segmentation alerts for unexpected traffic crossing into VoIP network segments
• Configure baseline monitoring for firmware versions and configuration states across all Fanvil devices
• Monitor for unusual reboot patterns or device behavior that may indicate compromise

How to Mitigate CVE-2025-64055

Immediate Actions Required

• Isolate Fanvil X210 devices on a dedicated VLAN with strict network access controls to limit exposure
• Implement firewall rules to restrict access to the device management interface to authorized administrator IP addresses only
• Audit all Fanvil X210 devices for signs of compromise including unauthorized configuration changes or firmware modifications
• Check the Fanvil Official Website for available firmware updates that address this vulnerability

Patch Information

At the time of this analysis, no vendor security advisory or specific patch information has been published. Organizations should monitor Fanvil's official website and the GitHub Security Advisory for updates regarding firmware patches that address CVE-2025-64055.

Workarounds

• Implement network segmentation to isolate Fanvil X210 devices from untrusted network segments
• Deploy web application firewall (WAF) rules or reverse proxy configurations to filter malicious requests targeting the management interface
• Disable remote management access if not required and manage devices only through physically connected administrative workstations
• Consider implementing 802.1X network access control to prevent unauthorized devices from accessing the network segment where Fanvil phones reside

# Example firewall rule to restrict management access (iptables)
# Replace 192.168.1.100 with your Fanvil device IP
# Replace 192.168.1.10 with authorized admin workstation IP
iptables -A INPUT -d 192.168.1.100 -p tcp --dport 80 -s 192.168.1.10 -j ACCEPT
iptables -A INPUT -d 192.168.1.100 -p tcp --dport 80 -j DROP
iptables -A INPUT -d 192.168.1.100 -p tcp --dport 443 -s 192.168.1.10 -j ACCEPT
iptables -A INPUT -d 192.168.1.100 -p tcp --dport 443 -j DROP