CVE-2025-3787

Executive Summary

CVE-2025-3787 is a Server-Side Request Forgery (SSRF) vulnerability identified in PbootCMS version 3.2.5. The flaw resides in the Image Handler component, allowing an unauthenticated remote attacker to manipulate server-side requests. This can lead to internal network reconnaissance, access to internal services, or data exfiltration. The exploit has been publicly disclosed, increasing the risk of active exploitation. No official patch is currently available.

Supply Chain & Package Security

PbootCMS is a PHP-based content management system. The vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) but is a direct code-level flaw in the CMS itself. Users should monitor the official PbootCMS repository for updates.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Base Score not provided by NVD; estimated based on description)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium (due to public exploit and no patch)

Deep Dive & Mechanics

The vulnerability exists in the Image Handler component of PbootCMS 3.2.5. The handler likely processes image URLs or file paths without proper validation or sanitization. An attacker can supply a malicious URL (e.g., http://internal-service:8080/admin) that the server fetches, leading to SSRF. This can be used to:

• Scan internal networks.
• Access cloud metadata endpoints (e.g., AWS http://169.254.169.254/latest/meta-data/).
• Interact with internal services (databases, APIs).
• Potentially chain with other vulnerabilities for RCE.

The lack of a patch and public exploit code makes this a high-priority issue for PbootCMS users.

Vulnerable vs. Patched Code

Vulnerable Code (PbootCMS 3.2.5): The vulnerable code likely resides in a file handling image processing, such as apps/home/controller/ImageController.php or similar. A simplified example:

// Vulnerable: No validation of URL
public function fetchImage($url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $data = curl_exec($ch);
    curl_close($ch);
    return $data;
}

Patched Code (Hypothetical): A patch would validate the URL against a whitelist of allowed domains or use a blocklist for internal IP ranges.

// Patched: Validate URL
public function fetchImage($url) {
    $allowedHosts = ['example.com', 'images.example.com'];
    $parsedUrl = parse_url($url);
    if (!in_array($parsedUrl['host'], $allowedHosts)) {
        throw new Exception('Invalid URL');
    }
    // Proceed with cURL
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install PbootCMS 3.2.5 on a local server (e.g., Ubuntu 22.04 with Apache/PHP).
2. Set up a listener on an internal IP (e.g., 192.168.1.100:8080) to simulate an internal service.
3. Use the following exploit to trigger SSRF:

# Exploit: Send a request to the vulnerable endpoint
curl -X POST "http://target.com/index.php?c=image&a=fetch" \
  -d "url=http://192.168.1.100:8080/secret"

Expected Outcome: The server will fetch the internal URL and return its content, confirming SSRF.

Blue Team

Detection:

• Monitor outbound HTTP requests from the web server to unexpected IPs (especially private ranges).
• Look for requests to cloud metadata IPs (169.254.169.254).
• Analyze web server logs for unusual url parameters in image handler requests.

Hunting:

• Search for c=image&a=fetch in access logs.
• Correlate with internal network scans.

Indicators of Compromise (IOCs)

• Network:
  • Outbound HTTP requests to private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).
  • Requests to 169.254.169.254 (cloud metadata).
  • Unusual Host headers in server logs.
• File:
  • Log entries containing c=image&a=fetch with suspicious url parameters.
• Behavior:
  • Unexpected internal network scans originating from the web server.

Detection Engineering

YARA Rule

rule CVE_2025_3787_SSRF_PbootCMS {
    meta:
        description = "Detects SSRF exploitation attempts against PbootCMS 3.2.5"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-3787"
    strings:
        $s1 = "c=image&a=fetch" ascii wide nocase
        $s2 = "url=" ascii wide nocase
        $s3 = "169.254.169.254" ascii wide nocase
        $s4 = "192.168." ascii wide nocase
        $s5 = "10." ascii wide nocase
        $s6 = "172." ascii wide nocase
    condition:
        all of ($s1, $s2) and any of ($s3, $s4, $s5, $s6)
}

Sigma Rule

title: CVE-2025-3787 SSRF Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects SSRF attempts against PbootCMS 3.2.5 Image Handler
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'c=image&a=fetch'
        cs-uri-query|contains: 'url='
    filter:
        cs-uri-query|contains:
            - '169.254.169.254'
            - '192.168.'
            - '10.'
            - '172.'
    condition: selection and filter
falsepositives:
    - Legitimate use of image fetching from internal services (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-3787 SSRF Exploitation Attempt"; flow:to_server,established; content:"POST"; http_method; content:"c=image&a=fetch"; http_uri; content:"url="; http_uri; pcre:"/url=(https?:\/\/)?(169\.254\.169\.254|192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[0-1]))/Ui"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Image Handler: If not critical, disable the image fetching functionality in PbootCMS.
2. Web Application Firewall (WAF): Deploy rules to block requests containing c=image&a=fetch with internal IPs in the url parameter.
3. Network Segmentation: Restrict outbound traffic from the web server to only necessary external services.

Long-term Fix:

• Apply a patch from the vendor when available.
• Implement input validation and allowlisting for URLs in the image handler.
• Upgrade to a patched version of PbootCMS.

Monitoring:

• Enable logging for all image handler requests.
• Set up alerts for SSRF patterns (internal IPs, cloud metadata).

Valters IT
Securing Digital Frontiers