Unauthenticated code execution via unsandboxed Twig prefill
Published Mar 30, 2026 · Updated Mar 30, 2026
Server-side template injection in Contact Form by Supsystic 1.7.36 and earlier allows remote attackers to execute OS commands. The cfsPreFill path copies GET parameter values into form fields and renders them with unsandboxed Twig_Loader_String; registerUndefinedFilterCallback() accepts attacker-selected PHP callbacks. A publicly reachable page containing a Supsystic form is enough to invoke PHP functions and execute commands without authentication or user interaction.
Summary
What happened
Server-side template injection in Contact Form by Supsystic 1.7.36 and earlier allows remote attackers to execute OS commands. The cfsPreFill path copies GET parameter values into form fields and renders them with unsandboxed Twig_Loader_String; registerUndefinedFilterCallback() accepts attacker-selected PHP callbacks. A publicly reachable page containing a Supsystic form is enough to invoke PHP functions and execute commands without authentication or user interaction.
The record
- CVE
- CVE-2026-4257
- Published
- Mar 30, 2026
- Updated
- Mar 30, 2026
- Vendor
- Supsystic
- Product
- Contact Form by Supsystic
- Classifications
- CWE-94, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 30, 2026CVE publishedPublication date reported by the CVE source.
- Mar 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=* <=1.7.36
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Metasploit Supsystic Contact Form RCE moduleweaponized · validated
- Supsystic Contact Form SSTI RCE proof of conceptfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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