Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
75Vexday Risk Score
Patch soon. It has a working public exploit.
ssvc Attendcvss 9.8epss 41%
from disclosure to weapon42 days
Published on NVDMar 30
1st PoC+42d
metasploitMar 30
exploitation probability
41%top 1% of all CVEs
observed exploitation
nono source reports it
3 public exploit(s)
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Affected products
supsysticcom · Contact Form by Supsysticpublic PoCs found — 3
exploitdbwww.exploit-db.com/exploits/52564unverifiedgithubgithub.com/dann3xplo1t/CVE-2026-4257★ 1githubgithub.com/shootcannon/CVE-2026-4257★ 0⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
References
https://plugins.trac.wordpress.org/browser/contact-form-by-supsystic/tags/1.7.36/modules/forms/views/forms.php#L323https://plugins.trac.wordpress.org/changeset/3491826/contact-form-by-supsystichttps://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=cve