How severe is CVE-2026-4257?

CVE-2026-4257 has a CVSS 3.1 base score of 9.8 (CRITICAL). EPSS estimates a 32.8% probability of exploitation in the next 30 days.

CVE-2026-4257: Contact Form by Supsystic <= 1.7.36

Q: What is CVE-2026-4257?

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 `regi

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.

Severity

CVSS 3.1 · CNA9.8 CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

SSVC · CISA-ADP

Exploitationnone

Automatableyes

Technical impacttotal

Affected Products

Vendor	Product	Affected versions
supsysticcom	Contact Form by Supsystic	0 to 1.7.36

References

3 Links

Other references

Record Details

Published

2026-03-30

Last updated

2026-04-08

Assigner (CNA)

Wordfence

Credited to

Azril Fathoni

Related Tool Categories

Tool categories that test for or protect against this vulnerability class.

CWE-94 · Code Injection

Application Security Tools Penetration Testing Tools

CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.