CVE-2026-4257
CriticalExploitedPublic exploitContact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
Published Mar 30, 2026 · Updated Apr 8, 2026 · Also known as 415c9658-bfb2-453b-a697-c63c08b0ca61
Key Facts
Patch immediately- CVE-2026-4257 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Contact Form by Supsystic (wordpress-plugin).
- It is exploited in the wild, listed in Industry KEV feed since Oct 13, 2026. Public exploit code is available.
- EPSS estimates a 33% probability of exploitation in the next 30 days.
- Fixed versions are available, including Contact Form by Supsystic 1.8.0.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
33%
Higher than 98.3% of all scored CVEs
Exploited in the wild
Yes
1 catalog listing
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2026-4257 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Oct 13, 2026 | n/a | Not reported |
Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected Products
2 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Contact Form by Supsysticwordpress-plugin | See advisory | 1.8.0 |
Patched Releases
Contact Form by Supsystic
1.8.0
Timeline
Publicly disclosed
Mar 30, 2026
Last updated
Apr 8, 2026
Added to Industry KEV feed
Oct 13, 2026
Weakness Type
- CWE-94 Improper Control of Generation of Code ('Code Injection')
References
- advisoryhttps://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=api-prod
- advisoryhttps://www.wordfence.com/threat-intel/vulnerabilities/id/415c9658-bfb2-453b-a697-c63c08b0ca61?source=api-scan
- exploitMSF wp_plugin_supsystic_contact_form_rce.rb
- exploitVulnCheck exploitation report
- exploitExploitDB-52564
FAQ
Common Questions.
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.
Affected: Contact Form by Supsystic (wordpress-plugin). The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Oct 13, 2026.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
Fixed versions are available, including Contact Form by Supsystic 1.8.0.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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