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CVE-2026-4257

CRITICAL 9.8 CVSS 3.1
Published
March 30, 2026
Last modified
June 17, 2026
NVD status
Deferred
Reported by
security@wordfence.com
Weakness
CWE-94
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Affected WordPress components

  • Contact Form by Supsystic Plugin · contact-form-by-supsystic
    Confirmed match Active
    Up to and including 1.7.36
    View on WordPress.org

A confirmed match is backed by the plugin or theme slug. A possible match is based on the product name only and should be verified.

Affected products and versions

  • supsysticcom Contact Form by Supsystic — Up to and including 1.7.36

References

  • plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/contact-form-by-supsystic/tags/1.7.36/modules/forms/views/forms.php#L323
  • plugins.trac.wordpress.org https://plugins.trac.wordpress.org/changeset/3491826/contact-form-by-supsystic
  • www.wordfence.com https://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=cve
  • nvd.nist.gov Official NVD record