CVE-2025-57633: FTP-Flask-python RCE Vulnerability

CVE-2025-57633 Overview

A command injection vulnerability exists in FTP-Flask-python through commit 5173b68 that allows unauthenticated remote attackers to execute arbitrary operating system commands. The vulnerability is located in the /ftp.html endpoint where the "Upload File" action constructs a shell command from the ftp_file parameter and executes it using os.system() without any sanitization or escaping. This represents a classic CWE-77 (Improper Neutralization of Special Elements used in a Command) vulnerability pattern.

Critical Impact

Unauthenticated remote attackers can achieve full system compromise by injecting arbitrary OS commands through the vulnerable file upload functionality, potentially leading to complete server takeover.

Affected Products

• FTP-Flask-python through commit 5173b68
• Python Flask applications using the vulnerable ftp_app.py module
• Systems exposing the /ftp.html endpoint without additional input validation

Discovery Timeline

• 2025-09-09 - CVE-2025-57633 published to NVD
• 2025-09-11 - Last updated in NVD database

Technical Details for CVE-2025-57633

Vulnerability Analysis

This command injection vulnerability stems from unsafe handling of user-supplied input in the FTP-Flask-python web application. The application accepts file upload requests through the /ftp.html endpoint and directly incorporates the ftp_file parameter into a shell command without any form of input validation, sanitization, or proper escaping.

The use of Python's os.system() function to execute the constructed command creates a direct pathway for attackers to inject and execute arbitrary operating system commands. Since the endpoint requires no authentication, any remote attacker with network access to the application can exploit this vulnerability to execute commands with the privileges of the web application process.

Root Cause

The root cause of this vulnerability is the improper neutralization of special elements used in a command (CWE-77). The application directly concatenates user-controlled input into a shell command string and passes it to os.system() for execution. This design flaw allows attackers to break out of the intended command context by injecting shell metacharacters such as semicolons (;), pipes (|), backticks, or command substitution syntax ($()).

The developer failed to implement any of the standard defenses against command injection, including:

• Input validation and allowlisting
• Proper escaping of shell metacharacters
• Use of safer alternatives like subprocess with shell=False
• Parameterized command execution

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can craft a malicious HTTP request to the /ftp.html endpoint with a specially crafted ftp_file parameter containing shell metacharacters and malicious commands. When the server processes this request, it executes both the intended command and the injected malicious payload.

For example, an attacker could inject commands to:

• Establish reverse shells for persistent access
• Exfiltrate sensitive data from the server
• Modify or delete files on the system
• Install additional malware or backdoors
• Pivot to other systems on the internal network

Technical details and example exploitation code can be found in the GitHub Gist security research. The vulnerable source code is available in the FTP-Flask-python repository.

Detection Methods for CVE-2025-57633

Indicators of Compromise

• Unusual process spawning from the Python/Flask web application process
• Shell metacharacters (;, |, $(), backticks) in HTTP request parameters to /ftp.html
• Unexpected outbound network connections from the web server
• Creation of new files or modification of system files by the web application user
• Evidence of reverse shell connections or unexpected interactive shell sessions

Detection Strategies

• Deploy web application firewalls (WAF) with rules to detect command injection patterns in HTTP parameters
• Monitor application logs for requests to /ftp.html containing suspicious characters or command sequences
• Implement endpoint detection and response (EDR) solutions to identify anomalous process execution chains
• Configure intrusion detection systems (IDS) to alert on network traffic patterns consistent with reverse shell activity

Monitoring Recommendations

• Enable detailed logging for the Flask application to capture all incoming request parameters
• Set up alerts for process execution anomalies where the web server spawns unexpected child processes
• Monitor for unusual file system activity in web application directories
• Implement network segmentation and monitor for lateral movement attempts from compromised web servers

How to Mitigate CVE-2025-57633

Immediate Actions Required

• Disable or restrict access to the /ftp.html endpoint immediately if the functionality is not business-critical
• Implement network-level access controls to limit who can reach the vulnerable endpoint
• Deploy a web application firewall with command injection protection rules in front of the application
• Audit logs for evidence of exploitation attempts or successful attacks

Patch Information

As of the last NVD update on 2025-09-11, no official patch has been released for this vulnerability. Organizations using FTP-Flask-python should consider the following remediation approaches:

1. Replace os.system() calls with subprocess.run() using shell=False and passing arguments as a list
2. Implement strict input validation using allowlists for acceptable filename characters
3. Use Python's shlex.quote() function to properly escape any user input that must be included in shell commands
4. Add authentication to the /ftp.html endpoint to limit attack surface

For technical reference, review the vulnerable code to understand the specific implementation that requires modification.

Workarounds

• Take the vulnerable application offline until a proper fix can be implemented
• Place the application behind a reverse proxy that strips or blocks requests containing shell metacharacters
• Implement application-level input sanitization by modifying ftp_app.py to validate the ftp_file parameter before use
• Run the Flask application in a containerized environment with minimal privileges to limit the impact of successful exploitation
• Use network segmentation to isolate the vulnerable application from critical infrastructure

# Example: Restrict access to vulnerable endpoint using iptables
# Allow only trusted IP ranges to access the web server
iptables -A INPUT -p tcp --dport 5000 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 5000 -j DROP