CVE-2026-4257

Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality

Published Mar 30, 2026 CVSS 3.1 · 9.8 Critical EPSS 41.5% KEV · Not listed

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.

Analysis

Technical impact

The Contact Form by Supsystic plugin for WordPress contains a Server‑Side Template Injection flaw that permits an unauthenticated attacker to inject and execute arbitrary Twig expressions. This vulnerability exposes the server to remote code execution, allowing execution of PHP functions and operating‑system commands. The weakness reflects code injection (CWE‑94).

Affected Systems

All WordPress installations using the Contact Form by Supsystic plugin version 1.7.36 or earlier are affected; the plugin is distributed by supsystic.com and is commonly embedded via their WordPress plugin.

Risk and Exploitability

The CVSS base score is 9.8, indicating critical severity. The EPSS score of 41% suggests a moderate likelihood of exploitation, and the vulnerability is not listed in the CISA KEV it over any public site without authentication by supplying crafted GET parameters to the prefill endpoint, triggering the Twig engine to process the injected template and run code. The exploitability is high and exhibits immediate remote code execution potential.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

supsysticcom

Contact Form by Supsystic

unaffected

Version	Status	Constraints
`0`	affected	≤ 1.7.36

No data.

Vendor Product Versions

Supsysticcom

Contact Form By Supsystic

Version	Status	Scheme	Platform
`[0,*]`	affected	generic	—

Wordpress

Version	Status	Scheme	Platform
`—`	unaffected	—	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade Contact Form by Supsystic to the latest release (1.7.37 or later) where the SSTI flaw has been fixed.
If an upgrade cannot be performed immediately, disable or delete the plugin from the WordPress site to remove the vulnerability.
Implement a web application firewall rule that blocks or sanitises GET parameters containing Twig delimiters ({{ or }}) to prevent script injection until the plugin can be updated.

Generated by OpenCVE AI on October 25, 2026 at 21:04 UTC.

Tracking

Advisories

No advisories available

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: 41.5% (41.475% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact total

References

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

History

Apr 1, 2026 2:15 AM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Supsysticcom Supsysticcom contact Form By Supsystic Wordpress Wordpress wordpress
Vendors & Products		Supsysticcom Supsysticcom contact Form By Supsystic Wordpress Wordpress wordpress

Mar 31, 2026 6:15 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Mar 31, 2026 3:00 AM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
Weaknesses		CWE-94
References		https://plugins.trac.wordpress.org/browser/contact-form-by-supsystic/tags/1.7.36/modules/forms/views/forms.php#L323 https://plugins.trac.wordpress.org/changeset/3491826/contact-form-by-supsystic https://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=cve
Metrics		cvssV3_1 `{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}`