CVE-2025-54757

Executive Summary

CVE-2025-54757 is an unrestricted file upload vulnerability affecting multiple versions of PowerCMS. The flaw allows authenticated product users to upload dangerous files (e.g., PHP, JavaScript, or other executable content). If a product administrator subsequently accesses such a malicious file, arbitrary script execution can occur in the administrator's browser, leading to potential cross-site scripting (XSS) or server-side code execution depending on the file type and server configuration. The CVSS score is 6.5 (Medium), and the EPSS probability is 0.0%, indicating low active exploitation in the wild. No public proof-of-concept (PoC) or exploit code is currently available. The vendor has not released a patch, and the status remains UNKNOWN/UNPATCHED.

Supply Chain & Package Security

PowerCMS is a proprietary content management system. No open-source package registries (NPM, PyPI, Go, Ruby) are associated with this product. Supply chain risk is limited to the vendor's distribution channels.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
• Base Score: 6.5 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs a valid user account.
• User Interaction (UI): Required (R) – Administrator must access the malicious file.
• Scope (S): Unchanged (U) – Vulnerability does not affect other components.
• Confidentiality (C): High (H) – Potential data exposure.
• Integrity (I): High (H) – Files can be modified.
• Availability (A): High (H) – System can be disrupted.

Threat Level: Medium. Exploitation requires authenticated user access and administrator interaction, reducing the likelihood of mass exploitation. However, the impact is severe if triggered.

Deep Dive & Mechanics

The vulnerability resides in the file upload functionality of PowerCMS. The application fails to validate the file type or content during upload, allowing users to submit files with dangerous extensions (e.g., .php, .asp, .jsp, .exe, .html, .svg). The uploaded file is stored on the server, typically in a web-accessible directory.

Attack Flow:

1. An authenticated user (e.g., content contributor) uploads a malicious file (e.g., shell.php or xss.html).
2. The file is stored on the server without sanitization.
3. An administrator navigates to the file's URL (e.g., https://target.com/uploads/shell.php).
4. If the file is a server-side script (e.g., PHP), it executes on the server, granting remote code execution (RCE).
5. If the file is client-side (e.g., HTML with JavaScript), it executes in the administrator's browser, leading to XSS, session hijacking, or further attacks.

Root Cause: Lack of file type validation, missing MIME type checks, and absence of content inspection. The application does not restrict uploads to safe extensions (e.g., images, documents) and does not rename or isolate uploaded files.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is described generically.

Vulnerable Code (PHP example):

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file"]["name"]);
move_uploaded_file($_FILES["file"]["tmp_name"], $target_file);
echo "File uploaded successfully.";
?>

This code does not check the file extension, MIME type, or content. Any file type is accepted.

Patched Code (Hypothetical):

<?php
$allowed_extensions = ['jpg', 'jpeg', 'png', 'gif', 'pdf'];
$target_dir = "uploads/";
$file_extension = strtolower(pathinfo($_FILES["file"]["name"], PATHINFO_EXTENSION));
if (!in_array($file_extension, $allowed_extensions)) {
    die("Invalid file type.");
}
$target_file = $target_dir . uniqid() . "." . $file_extension;
move_uploaded_file($_FILES["file"]["tmp_name"], $target_file);
echo "File uploaded successfully.";
?>

The patched version validates the extension against a whitelist and renames the file to prevent path traversal.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Valid user account on PowerCMS.
• Web server with PHP support (if targeting server-side execution).

Steps:

1. Log in to PowerCMS as a user with upload privileges.
2. Craft a malicious PHP file (e.g., shell.php):

   <?php system($_GET['cmd']); ?>
   

3. Upload the file via the file upload form.
4. Access the uploaded file URL (e.g., https://target.com/uploads/shell.php?cmd=id).
5. Observe command execution output.

Alternative (XSS):

1. Upload an HTML file containing JavaScript:

   <script>alert('XSS');</script>
   

2. When an administrator visits the file, the script executes.

No public exploit code is available for this CVE.

Blue Team (Defensive)

Detection:

• Monitor file upload logs for unusual extensions (e.g., .php, .exe, .html).
• Use WAF rules to block dangerous file types.
• Implement file integrity monitoring (FIM) on upload directories.

Prevention:

• Restrict upload directories to non-executable permissions (e.g., no +x on Linux).
• Use a reverse proxy to serve uploaded files with Content-Disposition: attachment headers.
• Deploy a Web Application Firewall (WAF) with rules to block script files in uploads.

Hunting:

• Search for recently uploaded files with extensions not in the allowed list.
• Review server access logs for requests to /uploads/ with query strings (e.g., ?cmd=).

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available – generate upon discovery)
• File Paths: /uploads/shell.php, /uploads/malicious.html
• Network Patterns: HTTP requests to /uploads/*.php?cmd=*
• Log Entries: POST /index.php?action=upload followed by GET /uploads/shell.php
• User Agents: Standard browser user agents (no specific pattern)

Detection Engineering

YARA Rule

rule PowerCMS_Unrestricted_Upload {
    meta:
        description = "Detects malicious files uploaded via PowerCMS CVE-2025-54757"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-54757"
    strings:
        $php_shell = "<?php system("
        $html_xss = "<script>"
        $dangerous_ext = ".php" nocase
    condition:
        ($php_shell or $html_xss) and $dangerous_ext
}

Sigma Rule

title: PowerCMS Unrestricted File Upload
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects upload of dangerous file types to PowerCMS
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/index.php'
        cs-uri-query: 'action=upload'
    condition: selection
fields:
    - c-ip
    - cs-uri-query
falsepositives:
    - Legitimate file uploads by administrators
level: medium

Suricata Rule

alert http any any -> any any (msg:"PowerCMS Unrestricted File Upload Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/index.php"; http_uri; content:"action=upload"; http_client_body; pcre:"/(\.php|\.exe|\.html|\.js)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable file uploads in PowerCMS until a patch is available.
2. Restrict upload directory permissions (e.g., chmod 644 on Linux, remove execute permission).
3. Implement a WAF rule to block uploads of executable files (e.g., .php, .asp, .exe).

Long-Term Fixes:

• Vendor Patch: Await an official patch from PowerCMS. Contact vendor for ETA.
• Code Hardening: If source code is accessible, implement file type whitelisting, MIME validation, and file renaming.
• Network Segmentation: Isolate the web server from critical internal networks.
• User Education: Train administrators to avoid accessing uploaded files directly.

Workaround:

• Use a reverse proxy (e.g., Nginx) to serve uploaded files with Content-Disposition: attachment and block script execution:

  location /uploads/ {
      add_header Content-Disposition 'attachment; filename="$1"';
      try_files $uri =404;
  }
  

Valters IT
DevSecOps & Cyber Threat Intelligence