Server-Side Template Injection in Contact Form by Supsystic for WordPress

CVE-2026-4257

What is CVE-2026-4257?

CVE-2026-4257 is a severe vulnerability found in the Contact Form by Supsystic plugin for WordPress, used to facilitate user interaction through contact forms on various websites. This vulnerability is classified as a Server-Side Template Injection (SSTI) flaw, allowing attackers to execute arbitrary server-side code. Specifically, the issue arises from the plugin's utilization of the Twig templating engine without appropriate sandboxing measures, coupled with a feature that enables prefilled form values through GET parameters. This allows unauthenticated users to inject malicious Twig expressions into form fields, leading to potential Remote Code Execution (RCE) on the server. The exploitation of this vulnerability poses significant risks to organizations, as it can compromise the integrity of web applications and lead to unauthorized access to sensitive data.

Potential impact of CVE-2026-4257

1. Remote Code Execution (RCE): Attackers can execute arbitrary PHP functions and operating system commands on the server, granting them full control over the host environment, which could lead to data loss or system manipulation.

2. Data Breach Risk: With the capability to execute commands remotely, attackers can potentially access sensitive information stored on the server, leading to data breaches that could expose user data and compliance violations.

3. Website Compromise and Service Disruption: Exploitation of this vulnerability may allow attackers to modify web content or take down websites, disrupting services for end-users and damaging an organization's online reputation.

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