CVE-2026-4257 in the critical feed json
Contact Form by Supsystic <= 1.7.36 - Unauthenticated Server-Side Template Injection via Prefill Functionality
published 7mo ago modified 4mo ago also EUVD-2026-17239
- cvss
- 9.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 41.5%
- EPSS 41.5% chance of exploitation in 30 days, percentile 98%
- public exploits
- 2
- Metasploit and Exploit-DB, plus a Nuclei check
Summary
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.
Is CVE-2026-4257 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerTimeline
- First public exploit (Metasploit exploit/multi/http/wp_plugin_supsystic_contact_form_rce)
- Published
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
- Assessed
- 7mo ago
Exploit prediction
41.48% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- Metasploit exploit/multi/http/wp_plugin_supsystic_contact_form_rce Supsystic Contact Form Wordpress Plugin SSTI RCE metasploit exploit, excellent rank, 2026-03-30
- EDB-52564 WordPress Plugin Supsystic Contact Form 1.7.36 - SSTI webapps, 2026-05-14
- Nuclei template WordPress Contact Form by Supsystic - Server-Side Template Injection nuclei detection template
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Affected products
- supsysticcom Contact Form by Supsystic
Classification
- Weakness
-
- CWE-94 Improper Control of Generation of Code
- Technology feeds
References
Sources
- CVE List CVE-2026-4257
- NVD CVE-2026-4257
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.