CVE-2026-4257
Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
- Published
- Mar 30, 2026
- Updated
- Apr 8, 2026
- Assigning CNA
- Wordfence
- Evidence observed
- May 14, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HModerate · next 30 days
- Percentile
- 98.3%
- Model date
- Oct 17, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
modules/exploits/multi/http/wp_plugin_supsystic_contact_form_rce.rb
Metasploit Framework modulesDeclared conditions
- platform: Linux,Unix,Windows($.exploit_multi/http/wp_plugin_supsystic_contact_form_rce.platform)
- verification: check_declared($.exploit_multi/http/wp_plugin_supsystic_contact_form_rce.check)
http/cves/2026/CVE-2026-4257.yaml
Nuclei TemplatesDeclared conditions
- network: http($.protocol_keys)
- verification: status,word($.matchers[*].type)
Responsible use
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