Home

Description

The Contact Form by Supsystic plugin for WordPress is vulnerable to Server-Side Template Injection (SSTI) leading to Remote Code Execution (RCE) in all versions up to, and including, 1.7.36. This is due to the plugin using the Twig `Twig_Loader_String` template engine without sandboxing, combined with the `cfsPreFill` prefill functionality that allows unauthenticated users to inject arbitrary Twig expressions into form field values via GET parameters. This makes it possible for unauthenticated attackers to execute arbitrary PHP functions and OS commands on the server by leveraging Twig's `registerUndefinedFilterCallback()` method to register arbitrary PHP callbacks.

PUBLISHED Reserved 2026-03-16 | Published 2026-03-30 | Updated 2026-04-08 | Assigner Wordfence




CRITICAL: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem types

CWE-94 Improper Control of Generation of Code ('Code Injection')

Product status

Default status
unaffected

Any version
affected

Timeline

2026-03-16:Vendor Notified
2026-03-30:Disclosed

Credits

Azril Fathoni finder

References

www.wordfence.com/...-bfb2-453b-a697-c63c08b0ca61?source=cve

plugins.trac.wordpress.org/.../modules/forms/views/forms.php

plugins.trac.wordpress.org/...1826/contact-form-by-supsystic

cve.org (CVE-2026-4257)

nvd.nist.gov (CVE-2026-4257)

Download JSON