CVE-2025-64056 Overview
CVE-2025-64056 is a file upload vulnerability affecting Fanvil X210 V2 IP phones running firmware version 2.12.20. The flaw allows unauthenticated attackers on the adjacent network to store arbitrary files on the device filesystem. The weakness is classified under CWE-306: Missing Authentication for Critical Function. Exploitation requires no user interaction and no privileges, but the attacker must be positioned on the local network segment. Successful exploitation impacts the integrity of the device by permitting attacker-controlled files to persist on the filesystem.
Critical Impact
Unauthenticated adjacent-network attackers can write arbitrary files to the Fanvil X210 filesystem, providing a foothold for further compromise of the IP phone.
Affected Products
- Fanvil X210 IP phone (hardware version 2.0)
- Fanvil X210 firmware version 2.12.20
- Deployments exposing the device management interface on internal networks
Discovery Timeline
- 2025-12-05 - CVE-2025-64056 published to NVD
- 2026-07-05 - Last updated in NVD database
Technical Details for CVE-2025-64056
Vulnerability Analysis
The Fanvil X210 firmware exposes a file upload function that does not enforce authentication before accepting and persisting uploaded content. An attacker on the same broadcast domain or routable adjacent network can submit files directly to the device without providing valid credentials. The uploaded content is written to the device filesystem, where it can be leveraged as a staging point for follow-on activity. Because the vulnerability affects a network-connected IP phone, the impact extends to any environment that trusts the device or reuses its network path.
Root Cause
The root cause is a missing authentication check on a file upload handler exposed by the device firmware. The handler processes upload requests based on their format alone without verifying that the requester holds a valid administrative session. This design flaw maps directly to CWE-306: Missing Authentication for Critical Function.
Attack Vector
The attack originates from the adjacent network, meaning the attacker must share the local network segment with the target phone. The attacker sends a crafted upload request to the device management interface. Because no authentication is required, the request is accepted and the payload is written to the device filesystem. The confidentiality impact is none, integrity impact is low, and availability impact is none, per the CVSS vector.
Refer to the GitHub Security Advisory for CVE-2025-64056 for the reporter's technical write-up.
Detection Methods for CVE-2025-64056
Indicators of Compromise
- Unexpected files appearing on the Fanvil X210 filesystem that do not correspond to vendor firmware artifacts or administrator activity.
- HTTP or HTTPS upload requests to the device management interface originating from workstations, servers, or unmanaged hosts on the voice VLAN.
- Configuration or ringtone files with unusual sizes, timestamps, or ownership on managed IP phones.
Detection Strategies
- Inspect network traffic to and from IP phone VLANs for unauthenticated POST or PUT requests targeting device upload endpoints.
- Baseline normal management traffic to Fanvil devices and alert on connections from hosts outside the provisioning server or administrator subnet.
- Correlate phone reboots, configuration changes, or new outbound connections with prior upload activity to identify potential compromise.
Monitoring Recommendations
- Forward switch and firewall logs covering voice VLANs into a central logging platform for retention and correlation.
- Enable NetFlow or IPFIX collection on switches serving IP phone segments to detect anomalous east-west flows.
- Track firmware and configuration hashes of deployed Fanvil X210 devices and alert on unauthorized changes.
How to Mitigate CVE-2025-64056
Immediate Actions Required
- Inventory all Fanvil X210 devices and identify units running firmware 2.12.20 or earlier.
- Restrict access to the device management interface using switch ACLs or firewall rules so only the provisioning server and administrator hosts can reach it.
- Segment IP phones onto a dedicated voice VLAN isolated from user workstations and guest networks.
- Review device filesystems for unexpected files and reset affected phones to a known-good configuration.
Patch Information
No vendor patch URL is listed in the enriched CVE data. Administrators should consult Fanvil support channels and the GitHub Security Advisory for CVE-2025-64056 for updated firmware availability and remediation guidance.
Workarounds
- Enforce network-layer access controls that block unauthenticated hosts from reaching the phone's HTTP and HTTPS management ports.
- Disable remote management interfaces on the device where operationally feasible.
- Require 802.1X authentication on switch ports serving voice endpoints to prevent unauthorized devices from joining the segment.
- Monitor for and alert on any file write activity to the device that does not originate from the sanctioned provisioning workflow.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
