CVE-2026-52889Network attack vector

Server-side template injection via Hidden defaults

Published Aug 19, 2026 · Updated Aug 19, 2026

Server-side template injection in Hidden fields in Verbb Formie before 3.1.27 allows remote attackers to execute server-side Twig expressions via request-derived defaults. In the Hidden field front-end render path, Hidden::getFrontEndInputOptions() copies request-derived values into defaultValue and sends them to Craft's Twig renderString path instead of treating them as plain text. Exploitation requires a public form that uses an affected request-backed Hidden default, and the resulting impact ranges from sensitive-data disclosure or state changes to remote code execution depending on exposed Twig capabilities.

CVSS severity9.8
Critical
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side template injection in Hidden fields in Verbb Formie before 3.1.27 allows remote attackers to execute server-side Twig expressions via request-derived defaults. In the Hidden field front-end render path, Hidden::getFrontEndInputOptions() copies request-derived values into defaultValue and sends them to Craft's Twig renderString path instead of treating them as plain text. Exploitation requires a public form that uses an affected request-backed Hidden default, and the resulting impact ranges from sensitive-data disclosure or state changes to remote code execution depending on exposed Twig capabilities.

The record

CVE
CVE-2026-52889
Published
Aug 19, 2026
Updated
Aug 19, 2026
Vendor
Verbb
Product
Formie
Classifications
CWE-1336, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.1.27

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Verbb · Formieversion=< 3.1.27

Published CVSS scores

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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1336Improper Neutralization of Special Elements Used in a Template Engine
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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