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VulnerabilityPublished

CVE-2026-52889: verbb/formie · Formie Hidden field defaults vulnerable to Server-Side Template Injection

Affects verbb/formieSource GCVE Database

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Authoritative record:CVE-2026-52889· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical : upgrade to 3.1.27 as a priority.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
1.2% chance of exploitation in 30 days – higher than 69% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.1.27
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade verbb/formie to 3.1.27.

Affected software

ProductAffectedFixed in
Packagistverbb/formieAffected
  • <3.1.27
Fixed in
  • 3.1.27

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary Formie Hidden fields could evaluate request-derived values as Twig during front-end form rendering. When a Hidden field used a dynamic default value such as HTTP User Agent, Referer URL, Current URL, Query Parameter, or Cookie Value, the value was copied from the incoming request and later passed to Craft’s Twig rendering layer. This allowed an unauthenticated attacker to provide Twig syntax in request-controlled input and have it evaluated server-side when the form was rendered. ## Affected Versions `verbb/formie` for Craft 5: - Affected: >= 3.0.0-beta.1, <= 3.1.26 - Patched: 3.1.27 ## Impact An unauthenticated attacker could trigger server-side template evaluation by visiting a public form containing a Hidden field configured with a request-derived default value. Because Craft’s normal Twig environment exposes application objects, this may lead to disclosure of sensitive information, modification of application state, or remote code execution depending on the site configuration and available Twig capabilities. ## Technical Details The issue exists in the Hidden field front-end render path. Request-derived Hidden field defaults were assigned to the field’s defaultValue, then rendered via Twig in `Hidden::getFrontEndInputOptions()`. The fix ensures Twig rendering is only performed for the custom default option, where the template source is admin-authored. Request-derived default options are now treated as plain strings. ## Patches Update to Formie 3.1.27 or later. ## Workarounds Until patched, avoid using request-derived Hidden field defaults on public forms, including: - HTTP User Agent - HTTP Refer URL - Current URL - Current URL without Query String - Query Parameter - Cookie Value Alternatively, remove affected Hidden fields from public forms until the update is applied. ## Credit Name: Yanchon918s Email: [ao9s@ao9s.net](mailto:ao9s@ao9s.net)

References

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