CVE-2025-34073: Maltrail RCE Vulnerability

CVE-2025-34073 Overview

An unauthenticated command injection vulnerability exists in stamparm/maltrail (Maltrail) versions <=0.54. A remote attacker can execute arbitrary operating system commands via the username parameter in a POST request to the /login endpoint. This occurs due to unsafe handling of user-supplied input passed to subprocess.check_output() in core/http.py, allowing injection of shell metacharacters. Exploitation does not require authentication and commands are executed with the privileges of the Maltrail process.

Critical Impact

This vulnerability allows unauthenticated remote code execution with no user interaction required. Attackers can fully compromise systems running vulnerable Maltrail instances, potentially leading to complete system takeover, data exfiltration, and lateral movement within the network.

Affected Products

• Maltrail versions <=0.54

Discovery Timeline

• 2025-07-02 - CVE CVE-2025-34073 published to NVD
• 2025-07-03 - Last updated in NVD database

Technical Details for CVE-2025-34073

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly referred to as OS Command Injection. The flaw exists in the authentication mechanism of Maltrail, specifically within the login functionality exposed at the /login endpoint.

The vulnerability stems from the application's failure to properly sanitize user-controlled input before passing it to operating system command execution functions. When a user submits login credentials, the username parameter value is incorporated into a command string that is subsequently executed via Python's subprocess.check_output() function. An attacker can inject shell metacharacters (such as ;, |, $(), or backticks) within the username field to break out of the intended command context and execute arbitrary system commands.

The existence of a Metasploit Maltrail RCE Exploit module demonstrates that this vulnerability has been weaponized and can be easily exploited by attackers with basic knowledge of penetration testing tools.

Root Cause

The root cause lies in the unsafe handling of user input within core/http.py. The application passes unsanitized user-supplied data directly to subprocess.check_output(), a function that invokes a shell to execute commands. Without proper input validation, escaping, or parameterized command execution, shell metacharacters in the username field are interpreted by the underlying shell, allowing command injection.

The proper remediation would involve either using parameterized command execution (avoiding shell=True), implementing strict input validation with an allowlist of permitted characters, or escaping special shell characters before command execution.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker sends a crafted HTTP POST request to the vulnerable /login endpoint with a malicious payload in the username parameter. The payload contains shell metacharacters followed by arbitrary commands.

For example, an attacker could inject commands that establish a reverse shell, download and execute malware, or exfiltrate sensitive data from the compromised system. Since the commands execute with the privileges of the Maltrail process, the impact depends on how Maltrail is deployed—if running as root, complete system compromise is achieved immediately.

Technical details and proof-of-concept information can be found in the Huntr Bounty Listing and the VulnCheck Maltrail RCE Advisory.

Detection Methods for CVE-2025-34073

Indicators of Compromise

• Unusual HTTP POST requests to /login endpoints containing shell metacharacters (;, |, &, $(), backticks) in the username field
• Unexpected child processes spawned by the Maltrail process (e.g., /bin/sh, /bin/bash, wget, curl, nc)
• Network connections initiated by the Maltrail process to external IP addresses not associated with normal threat intelligence operations
• Log entries showing login attempts with malformed or unusually long username values containing special characters

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block command injection patterns in POST parameters to the /login endpoint
• Implement network-based intrusion detection signatures for Maltrail exploitation attempts, monitoring for characteristic payload patterns
• Configure endpoint detection to alert on suspicious process chains where the Maltrail service spawns unexpected shell processes
• Monitor application logs for authentication failures with anomalous username patterns that include shell metacharacters

Monitoring Recommendations

• Enable detailed HTTP request logging on servers hosting Maltrail, capturing full POST body content for forensic analysis
• Configure SentinelOne Singularity to monitor process behavior and detect command injection exploitation attempts through behavioral analysis
• Implement SIEM correlation rules to identify patterns of exploitation attempts across multiple Maltrail instances
• Establish baseline network behavior for Maltrail instances and alert on anomalous outbound connections

How to Mitigate CVE-2025-34073

Immediate Actions Required

• Immediately restrict network access to Maltrail instances, limiting exposure to trusted networks only
• If Maltrail is not essential, consider temporarily disabling the service until a patched version is deployed
• Implement network segmentation to isolate systems running Maltrail from critical infrastructure
• Review system logs for signs of prior exploitation and conduct forensic analysis if compromise indicators are detected

Patch Information

Organizations should monitor the GitHub Maltrail Project for security updates addressing this vulnerability. The issue is tracked in GitHub Issue #19146. Upgrade to a version greater than 0.54 once a patched release becomes available.

Workarounds

• Place Maltrail behind a reverse proxy with strict input validation rules that reject requests containing shell metacharacters in POST parameters
• Implement network-level access controls (firewall rules, VPN requirements) to ensure only authorized administrators can reach the Maltrail login endpoint
• Run Maltrail with minimal privileges using a dedicated service account to limit the impact of successful exploitation
• Deploy a Web Application Firewall (WAF) with command injection detection rules as an additional layer of defense

# Example: Restrict access to Maltrail with iptables
# Allow only trusted management network to access Maltrail
iptables -A INPUT -p tcp --dport 8338 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8338 -j DROP