CVE-2025-24346

Executive Summary

CVE-2025-24346 is a high-severity vulnerability (CVSS 7.5) affecting the web application proxy functionality of ctrlX OS, a real-time operating system used in industrial automation and IoT devices. A remote authenticated attacker with low privileges can craft an HTTP request to manipulate the /etc/environment file, leading to persistent environment variable changes. This can enable privilege escalation, service hijacking, or persistent backdooring of the system. No public exploit or patch is currently available, but the attack vector is clear and dangerous in OT/ICS environments.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs only low-privileged access.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality (C): None (N) – No direct data theft.
• Integrity (I): High (H) – Full control over environment variables, affecting system behavior.
• Availability (A): None (N) – No direct denial of service.

Threat Level: High – Low barrier to entry, high integrity impact, and potential for lateral movement in OT networks.

Deep Dive & Mechanics

The vulnerability resides in the Proxy functionality of the ctrlX OS web application. The proxy endpoint does not properly sanitize or validate user-supplied input when processing HTTP requests. By sending a crafted request (e.g., with a malicious Host header or path traversal), an authenticated low-privileged user can write arbitrary content to /etc/environment.

Attack Flow:

1. Authenticate to the ctrlX web interface with low-privileged credentials.
2. Send a specially crafted HTTP request to the proxy endpoint (e.g., POST /proxy with Host: 127.0.0.1 and a body containing PATH=/malicious:$PATH).
3. The proxy writes the payload to /etc/environment without validation.
4. On next system boot or service restart, the malicious environment variables are loaded, potentially altering PATH, LD_PRELOAD, or other critical variables.

Impact:

• Privilege Escalation: By modifying LD_PRELOAD, an attacker can load a malicious shared library into privileged processes.
• Persistence: Environment variables survive reboots, providing a stealthy backdoor.
• Service Hijacking: Changing PATH can cause services to execute attacker-controlled binaries.

Vulnerable vs. Patched Code

No patch is available. The vulnerable code likely resembles:

# Vulnerable pseudo-code
def proxy_handler(request):
    env_file = open("/etc/environment", "a")
    env_file.write(request.body)  # No sanitization
    env_file.close()

A patched version would:

# Patched pseudo-code
def proxy_handler(request):
    allowed_keys = ["HTTP_PROXY", "HTTPS_PROXY", "NO_PROXY"]
    for line in request.body.splitlines():
        key, _, value = line.partition("=")
        if key.strip() in allowed_keys:
            env_file.write(f"{key}={value}\n")
    env_file.close()

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Low-privileged credentials for ctrlX OS web interface.
• Network access to the ctrlX device (port 443 or 80).

Exploit Steps:

1. Authenticate and obtain a session cookie.
2. Send a crafted POST request to the proxy endpoint:

curl -X POST https://target-ctrlx/proxy \
  -H "Cookie: session=valid_session" \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "LD_PRELOAD=/tmp/malicious.so"

3. Upload a malicious shared library to /tmp/malicious.so via another vulnerable endpoint.
4. Trigger a service restart (e.g., via sudo reboot if possible, or wait for natural reboot).

Alternative Payload:

curl -X POST https://target-ctrlx/proxy \
  -H "Cookie: session=valid_session" \
  -d "PATH=/tmp/evil:$PATH"

Blue Team (Detection & Hardening)

Detection:

• Monitor /etc/environment for unauthorized changes using file integrity monitoring (e.g., AIDE, Tripwire).
• Alert on any HTTP requests to the proxy endpoint with unusual body content (e.g., containing LD_PRELOAD, PATH=, etc.).
• Correlate authentication logs with proxy access logs.

Hardening:

• Restrict access to the proxy endpoint to only trusted IPs.
• Implement strict input validation on the proxy handler.
• Use SELinux or AppArmor to prevent unauthorized writes to /etc/environment.
• Apply principle of least privilege: revoke low-privileged accounts if not needed.

Indicators of Compromise (IOCs)

• File: /etc/environment containing unexpected entries like LD_PRELOAD, PATH=/tmp/, or HTTP_PROXY=.
• Process: Unusual processes loading libraries from /tmp/ or other writable directories.
• Network: HTTP requests to /proxy with body containing environment variable assignments.
• Logs: Syslog entries showing LD_PRELOAD or PATH modifications in environment.

Detection Engineering

YARA Rule

rule cve_2025_24346_env_manipulation {
    meta:
        description = "Detects attempts to manipulate /etc/environment via ctrlX proxy"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-24346"
    strings:
        $env_var = /(LD_PRELOAD|LD_LIBRARY_PATH|PATH|HTTP_PROXY|HTTPS_PROXY|NO_PROXY)\s*=\s*/ nocase
        $proxy_path = "/proxy"
    condition:
        $proxy_path and $env_var
}

Sigma Rule

title: CVE-2025-24346 - ctrlX OS Environment Manipulation via Proxy
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests to ctrlX proxy endpoint with environment variable manipulation payloads
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/proxy'
    keywords:
        - 'LD_PRELOAD'
        - 'LD_LIBRARY_PATH'
        - 'PATH='
        - 'HTTP_PROXY='
        - 'HTTPS_PROXY='
        - 'NO_PROXY='
    condition: selection and keywords
falsepositives:
    - Legitimate proxy configuration changes by administrators
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-24346 - ctrlX OS Environment Manipulation via Proxy";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/proxy"; http_uri;
    content:"LD_PRELOAD"; nocase; http_client_body;
    sid:1000001;
    rev:1;
    reference:cve,2025-24346;
    classtype:attempted-admin;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the proxy functionality if not required for operations.
2. Restrict network access to the ctrlX web interface using firewall rules.
3. Change all low-privileged credentials and enforce strong password policies.

Long-term Fix:

• Apply vendor patch when released (monitor Bosch Rexroth security advisories).
• Implement input validation on the proxy endpoint to allow only safe environment variables.
• Use file integrity monitoring on /etc/environment and other critical system files.

Workaround:

• Mount /etc/environment as read-only using chattr +i /etc/environment (requires root).
• Deploy a WAF rule to block requests containing environment variable patterns.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst