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CVE-2026-4257

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

Published: Mar 30, 2026Updated: Apr 24, 2026 Sources: CVE List NVDCWE-94
NVD MITRE
9.8CVSSCRITICAL
EPSS Score
41.5%
Top 1.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
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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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-94

Affected Products

Contact Form by Supsysticsupsysticcom
On-prem
Web & CMS Plugins / wordpress-plugin
supsysticcomcommercialWeb & CMS Pluginsaka supersysticcom, supersystic

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

2 techniques
Execution
Initial Access
View detailed technique mapping

References

https://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=cve
wordfence.com
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
plugins.trac.wordpress.org

Timeline

Published
Mar 30, 2026
Last Updated
Apr 24, 2026
News mentions
1

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