CVE-2025-6691

Executive Summary

CVE-2025-6691 is a critical vulnerability in the SureForms – Drag and Drop Form Builder for WordPress plugin, affecting all versions up to and including 1.7.3. The flaw resides in the delete_entry_files() function, which performs insufficient file path validation. This allows an unauthenticated attacker to delete arbitrary files on the server. While the immediate impact is data loss or service disruption, the most severe consequence is the potential for remote code execution (RCE) by deleting critical files such as wp-config.php, which would force WordPress into a setup state and allow an attacker to inject malicious configuration. As a WordPress plugin vulnerability, it is part of the broader WordPress ecosystem and does not involve Apache or Nginx directly.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin from the repository are at risk. There is no known supply chain compromise of the plugin itself, but the lack of a patch increases the risk of exploitation in the wild.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: High
• Availability Impact: High

The high integrity and availability impacts, combined with the lack of authentication requirements, make this a severe threat. An attacker can delete arbitrary files, potentially leading to complete site takeover.

Deep Dive & Mechanics

The vulnerability exists in the delete_entry_files() function within the SureForms plugin. This function is intended to delete files associated with form entries. However, it fails to properly validate the file path provided by the user. Specifically, it does not check for path traversal sequences (e.g., ../) or ensure that the file to be deleted is within the intended upload directory.

The function likely accepts a file path parameter from an HTTP request (e.g., via AJAX or REST API) and passes it directly to a file deletion function like unlink() or wp_delete_file() without sanitization. An attacker can craft a request with a path like ../../wp-config.php to delete the WordPress configuration file. Deleting wp-config.php forces WordPress to re-run the installation wizard, allowing an attacker to set up a new database connection and gain administrative access.

The attack flow:

1. Attacker sends a POST request to the vulnerable endpoint with a crafted file_path parameter.
2. The plugin's delete_entry_files() function receives the path and deletes the file.
3. If wp-config.php is deleted, the site becomes unconfigured.
4. Attacker visits the site's installation page (/wp-admin/install.php) and sets up a new database with their own credentials.
5. Attacker logs in as admin and achieves RCE via plugin/theme installation or code injection.

Vulnerable vs. Patched Code

Vulnerable Code (SureForms <= 1.7.3):

function delete_entry_files($entry_id, $file_path) {
    // No validation of $file_path
    if (file_exists($file_path)) {
        unlink($file_path);
    }
}

Patched Code (Hypothetical):

function delete_entry_files($entry_id, $file_path) {
    $upload_dir = wp_upload_dir();
    $allowed_path = $upload_dir['basedir'] . '/sureforms/';
    $real_path = realpath($file_path);
    $real_allowed = realpath($allowed_path);
    
    // Ensure the file is within the allowed directory
    if (strpos($real_path, $real_allowed) === 0 && file_exists($real_path)) {
        unlink($real_path);
    }
}

The patched version uses realpath() to resolve any path traversal and then checks that the resolved path starts with the allowed upload directory. This prevents deletion of files outside the intended scope.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install WordPress on a local server (e.g., using XAMPP or Docker).
2. Install SureForms plugin version 1.7.3.
3. Create a form and submit an entry to generate an entry ID.

Exploitation Steps:

1. Identify the vulnerable endpoint. Typically, it is an AJAX action like sureforms_delete_entry_file or a REST API endpoint.
2. Craft a POST request to delete wp-config.php:

   POST /wp-admin/admin-ajax.php HTTP/1.1
   Host: target-site.com
   Content-Type: application/x-www-form-urlencoded
   
   action=sureforms_delete_entry_file&entry_id=1&file_path=../../wp-config.php
   

3. Verify deletion by checking if the site redirects to the installation page.
4. Visit /wp-admin/install.php and set up a new database with attacker-controlled credentials.
5. Log in as admin and install a malicious plugin to achieve RCE.

Note: No public exploit code is available at this time.

Blue Team (Defensive)

Detection:

• Monitor for unusual file deletion requests, especially those containing path traversal sequences (../).
• Alert on requests to admin-ajax.php or REST API endpoints with parameters like file_path containing wp-config.php or other critical files.
• Use file integrity monitoring (FIM) to detect deletion of critical files.

Mitigation:

• Immediately disable the SureForms plugin if no patch is available.
• Implement a Web Application Firewall (WAF) rule to block requests with path traversal patterns.
• Restrict file permissions so that the web server cannot delete critical files (e.g., chmod 444 wp-config.php).

Indicators of Compromise (IOCs)

• File Paths: wp-config.php, .htaccess, wp-content/debug.log
• HTTP Requests: POST requests to /wp-admin/admin-ajax.php with action=sureforms_delete_entry_file and file_path parameter containing ../
• Log Entries: PHP error logs showing unlink() failures or WordPress installation page access.
• Network: Outbound connections from the server to attacker-controlled hosts after site takeover.

Detection Engineering

YARA Rule

rule CVE_2025_6691_SureForms_File_Deletion {
    meta:
        description = "Detects attempts to exploit CVE-2025-6691 in SureForms plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-6691"
    strings:
        $sureforms_action = "sureforms_delete_entry_file"
        $path_traversal = "../"
        $wp_config = "wp-config.php"
    condition:
        $sureforms_action and ($path_traversal or $wp_config)
}

Sigma Rule

title: CVE-2025-6691 SureForms Arbitrary File Deletion
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects exploitation attempts of CVE-2025-6691 via HTTP requests
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=sureforms_delete_entry_file'
        cs-uri-query|contains: 'file_path='
    condition: selection
falsepositives:
    - Legitimate plugin functionality (if any)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-6691 SureForms File Deletion Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=sureforms_delete_entry_file"; http_client_body; content:"file_path="; http_client_body; pcre:"/\.\.\//"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the SureForms plugin until a patch is released.
2. Set wp-config.php permissions to 444 (read-only) to prevent deletion by the web server user.
3. Implement a WAF rule to block requests containing sureforms_delete_entry_file and path traversal sequences.

Long-term Fix:

• Monitor the SureForms plugin repository for a patched version (expected to be > 1.7.3).
• Apply the patch as soon as it becomes available.
• Conduct a security audit of all WordPress plugins for similar vulnerabilities.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.