CVE-2025-6625: FTP Service DoS Vulnerability

CVE-2025-6625 Overview

CVE-2025-6625 is a CWE-20: Improper Input Validation vulnerability that exists in Schneider Electric devices. This vulnerability could cause a Denial of Service (DoS) condition when a specifically crafted FTP command is sent to the affected device. Attackers exploiting this vulnerability can disrupt device operations by sending malicious FTP commands over the network, requiring no authentication or user interaction.

Critical Impact

Attackers can remotely disrupt operations of affected Schneider Electric industrial devices by sending specially crafted FTP commands, potentially impacting critical infrastructure availability.

Affected Products

• Schneider Electric industrial devices with FTP service enabled (see vendor advisory for specific model numbers)

Discovery Timeline

• 2025-08-18 - CVE-2025-6625 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-6625

Vulnerability Analysis

This vulnerability stems from improper input validation within the FTP service implementation on affected Schneider Electric devices. The device fails to adequately validate and sanitize FTP commands received from network clients before processing them. When a specially crafted FTP command containing unexpected or malicious input is sent to the device, the FTP service cannot properly handle the malformed data, resulting in a Denial of Service condition.

The vulnerability is exploitable over the network without requiring authentication or any user interaction, making it particularly dangerous for internet-exposed or inadequately segmented industrial control systems. Successful exploitation results in service disruption that may require manual intervention or device restart to restore normal operations.

Root Cause

The root cause of CVE-2025-6625 is the lack of proper input validation in the FTP command parser. The affected FTP service does not implement adequate bounds checking or input sanitization when processing incoming FTP commands. This allows an attacker to craft malicious FTP commands that trigger an unhandled exception or resource exhaustion, leading to service failure.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker with network access to the FTP service (typically TCP port 21) can send specially crafted FTP commands to exploit this vulnerability. The attack requires:

1. Network connectivity to the target device's FTP service
2. Knowledge of the FTP protocol to craft malicious commands
3. No authentication credentials are required
4. No user interaction is necessary

The exploitation results in a Denial of Service condition affecting the FTP service and potentially the broader device functionality, impacting the integrity of device operations in industrial control environments.

Detection Methods for CVE-2025-6625

Indicators of Compromise

• Unexpected FTP service crashes or restarts on affected Schneider Electric devices
• Anomalous FTP traffic patterns including malformed or unusually long FTP commands
• Device availability issues coinciding with FTP connection attempts from unknown sources
• Error logs indicating FTP command parsing failures or unhandled exceptions

Detection Strategies

• Implement network intrusion detection rules to identify malformed FTP commands targeting Schneider Electric devices
• Monitor FTP service logs for repeated connection attempts followed by service failures
• Deploy protocol-aware network monitoring to detect anomalous FTP command structures
• Establish baseline FTP traffic patterns and alert on deviations

Monitoring Recommendations

• Enable detailed logging on FTP services and forward logs to a SIEM for correlation
• Implement network traffic analysis on segments containing affected industrial devices
• Set up availability monitoring with alerts for FTP service disruptions
• Review firewall logs for unauthorized FTP connection attempts from external networks

How to Mitigate CVE-2025-6625

Immediate Actions Required

• Disable FTP service on affected devices if not operationally required
• Implement network segmentation to restrict FTP access to authorized management systems only
• Apply firewall rules to block FTP traffic (TCP port 21) from untrusted networks
• Review and apply security patches from Schneider Electric as they become available

Patch Information

Schneider Electric has released a security notice addressing this vulnerability. Organizations should refer to the Schneider Electric Security Notice SEVD-2025-224-05 for detailed patch information, affected product versions, and remediation guidance specific to their deployed devices.

Workarounds

• Disable the FTP service entirely if not required for device operations
• Restrict network access to the FTP service using firewall rules and access control lists
• Implement network segmentation to isolate affected devices from untrusted networks
• Use VPN or other secure tunneling mechanisms for remote FTP access if required
• Monitor device availability and implement automated restart procedures as an interim measure

# Example firewall configuration to restrict FTP access
# Allow FTP only from authorized management subnet
iptables -A INPUT -p tcp --dport 21 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP