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CVE-2026-4257— Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality

Quick assessment

Affected
supsysticcom Contact Form by Supsystic
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress和WordPress plugin都是WordPress基金会的产品。WordPress是一套使用PHP语言开发的博客平台。该平台具有在基于PHP和MySQL的服务器上架设个人博客网站的功能。WordPress plugin是一个应用插件。 WordPress plugin Contact Form by Supsystic 1.7.36及之前版本存在代码注入漏洞，该漏洞源于使用未沙箱化的Twig模板引擎且未经验证的用户可通过GET参数注入任意Twig表达式，可能导致服务器端模板注入和远

CVSS 9.8 · Critical EPSS 32.78% · P98
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I. Basic Information for CVE-2026-4257

Vulnerability Information
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Vulnerability Title
Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Vulnerability Title
WordPress plugin Contact Form by Supsystic 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
WordPress和WordPress plugin都是WordPress基金会的产品。WordPress是一套使用PHP语言开发的博客平台。该平台具有在基于PHP和MySQL的服务器上架设个人博客网站的功能。WordPress plugin是一个应用插件。 WordPress plugin Contact Form by Supsystic 1.7.36及之前版本存在代码注入漏洞，该漏洞源于使用未沙箱化的Twig模板引擎且未经验证的用户可通过GET参数注入任意Twig表达式，可能导致服务器端模板注入和远
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
supsysticcom Contact Form by Supsystic * ~ 1.7.36 -

II. Public POCs for CVE-2026-4257

# POC Description Source Link Shenlong Link
1 Contact Form by Supsystic WordPress plugin <= 1.7.36 contains a server-side template injection caused by unsandboxed Twig_Loader_String and cfsPreFill functionality, letting unauthenticated attackers execute arbitrary code remotely via GET parameters. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-4257.yaml POC Details
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III. Intelligence Information for CVE-2026-4257

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Patches & Fixes for CVE-2026-4257 (1)

IV. Related Vulnerabilities

Same product: Contact Form by Supsystic
Same vendor: supsysticcom
Same weakness: CWE-94

V. Comments for CVE-2026-4257

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