dbcve.org
Code InjectionWeakness · CWE-94

CVE-2026-4257

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Contact Form by Supsystic WordPress plugin (versions up to 1.7.36) is vulnerable to unauthenticated Server-Side Template Injection (SSTI) leading to Remote Code Execution. The plugin uses the Twig `Twig_Loader_String` template engine without sandboxing, and the `cfsPreFill` prefill functionality allows attackers to inject arbitrary Twig expressions via GET parameters. Attackers can execute arbitrary PHP functions and OS commands by leveraging Twig's `registerUndefinedFilterCallback()` method.

MitigationImmediately update the plugin to a version beyond 1.7.36 if available, or disable/delete the plugin until a patch is released. Investigate server logs for indicators of compromise given the RCE capability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify plugin is installed
    Check the WordPress plugin directory for the Contact Form by Supsystic plugin. In WordPress admin, go to Plugins > Installed Plugins and look for 'Contact Form by Supsystic' or check the file system at wp-content/plugins/contact-form-by-supsystic/
    Affected if The plugin is present on the WordPress installation
  2. Check installed plugin version
    In WordPress admin, go to Plugins > Installed Plugins and find the version number listed for Contact Form by Supsystic. Alternatively, check the main plugin file header in wp-content/plugins/contact-form-by-supsystic/contact-form-by-supsystic.php for the 'Version' tag
    Affected if The installed version is 1.7.36 or lower (any version up to and including 1.7.36)
  3. Confirm cfsPreFill functionality is active
    Review the plugin settings or configuration to determine if the prefill functionality is enabled. Check plugin admin pages for any settings related to 'prefill' or 'cfsPreFill'. Inspect plugin source code for references to 'cfsPreFill' or 'prefill' to verify the feature exists in the installed version
    Affected if The cfsPreFill feature is present and accessible in the installed version
  4. Inspect HTTP logs for injection attempts
    Review web server access logs and WordPress debug logs for suspicious GET requests containing Twig-like patterns such as '{{', '|', 'registerUndefinedFilterCallback', or shell execution functions. Search for requests to paths like /?cfsPreFill= or similar parameter patterns
    Affected if Logs contain requests with Twig template syntax or attempts to leverage registerUndefinedFilterCallback in cfsPreFill parameters

A WordPress site is affected if it has the Contact Form by Supsystic plugin installed with version 1.7.36 or lower and the cfsPreFill prefill functionality is accessible, allowing unauthenticated attackers to inject malicious Twig expressions via GET parameters.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Immediately update the plugin to a version beyond 1.7.36 if available, or disable/delete the plugin until a patch is released. Investigate server logs for indicators of compromise given the RCE capability.

Recommended fix High confidence

Contact Form by Supsystic version 1.7.37 or latest available version (version after 1.7.36)

  1. 1. Check the current version of the Contact Form by Supsystic plugin installed on your WordPress site
  2. 2. Navigate to Plugins > Installed Plugins in the WordPress admin dashboard
  3. 3. Locate the Contact Form by Supsystic plugin
  4. 4. If the installed version is 1.7.36 or earlier, update the plugin to the latest available version
  5. 5. Verify the update was successful by confirming the new version number after updating
  6. 6. Test form functionality to ensure the update did not break existing forms
  7. 7. Consider reviewing the plugin's changelog to confirm the security fix is included in the new version
Caveat Review plugin changelog before upgrading; major version jumps may include feature changes that could affect form configurations

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-4257 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data