CVE-2026-4257
high-risk
Published 2026-03-30
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.
Do I need to act?
!
19.6% chance of exploitation in next 30 days
EPSS score — higher than 80% of all CVEs
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
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Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
9
CVSS 9.8/10
Critical
NETWORK
/ LOW complexity
51
/ 100
high-risk
Severity
32/34 · Critical
Exploitability
14/34 · Moderate
Exposure
5/34 · Minimal