Drag and Drop Multiple File Upload for Contact Form 7 <= 1.3.9.7 - Unauthenticated Arbitrary File Upload via Non-ASCII Filename Blacklist Bypass

Summary

The Drag and Drop Multiple File Upload for Contact Form 7 plugin for WordPress is vulnerable to arbitrary file upload in versions up to, and including, 1.3.9.7. This is due to insufficient file type validation that occurs when custom blacklist types are configured, which replaces the default dangerous extension denylist instead of merging with it, and the wpcf7_antiscript_file_name() sanitization function being bypassed for filenames containing non-ASCII characters. This makes it possible for unauthenticated attackers to upload arbitrary files, such as PHP files, to the server, which can be leveraged to achieve remote code execution. The vulnerability was originally reported by Leonid Semenenko (lsemenenko) and partially patched in version 1.3.9.7. A bypass for the patch was separately discovered and reported by Nguyen Hung (Mitchell).

Timeline

1. Apr 17, 2026, 5:25 PM UTCCVE published
2. Apr 17, 2026, 6:34 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. May 27, 2026, 12:26 AM UTCRecord last updated

Affected versions

• glenwpcoder Drag and Drop Multiple File Upload for Contact Form 7

  through 1.3.9.7

References 12