Formie: Server-Side Template Injection in Formie Hidden field defaults

published 2026-07-06 4 mo ago modified 2026-09-10 59 d ago also GHSA-565m-g33j-jq96 , EUVD-2026-62518

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.3%; EPSS 1.3% chance of exploitation in 30 days, percentile 70%
public exploits: 0; none known

Formie is a Craft CMS plugin for creating forms. Prior to 3.1.27, Formie can pass request-derived Hidden field defaults such as HTTP User Agent, Referer URL, Current URL, Current URL without Query String, Query Parameter, and Cookie Value to Craft's Twig rendering layer during front-end form rendering. An unauthenticated attacker can place Twig syntax in one of these request-controlled inputs when a public form contains an affected Hidden field. Hidden::getFrontEndInputOptions() then assigns the value to defaultValue and calls renderString, causing server-side template evaluation rather than treating the request data as a plain string. Depending on the Craft site configuration and available Twig capabilities, exploitation can disclose sensitive information, modify application state, or achieve remote code execution. This issue is fixed in version 3.1.27.

Patch / fix

fixed in 1 links 2

packagist verbb/formie 3.1.27

github.com/verbb/formie@d3b9d15 commit
github.com/verbb/formie/releases/tag/3.1.27 release

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 2 mo ago (2026-08-19)

Exploit prediction

1.27% chance of exploitation in the next 30 days, higher than 70% of all scored CVEs (FIRST EPSS, 2026-11-08).

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
GitHub	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
packagist	verbb/formie	<3.1.27	3.1.27

Affected products

verbb formie

Classification

Weakness

CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine

References

Sources

Fencer Vulns 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.

Summary