Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder < 7.0 - Unauthenticated Denial of Service
Strategic Overview
- Status
- Patched in 7.0
- Affected Plugin
- Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder
- Affected Version
< 7.0- CVSS
- 7.5High
- Weakness type
- CWE-400 · Uncontrolled Resource Consumption
- CVE
CVE-2026-85642
At a glance
CVE-2026-85642 is a high-severity Uncontrolled Resource Consumption vulnerability in the Formidable Forms WordPress plugin, affecting versions < 7.0. It carries a CVSS score of 7.5 (reachable over the network; low attack complexity; high availability impact). Exploitation requires no authentication. The issue is fixed in version 7.0; sites on affected versions should update now. Disclosed October 2026, reported by Naoki Kawahigashi.
Vulnerability Overview
The Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder plugin for WordPress is vulnerable to Denial of Service in all versions up to 7.0. This is due to insufficient validation of user supplied input. This makes it possible for unauthenticated attackers to make the affected site unavailable.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on availability.
CWE-400: Uncontrolled Resource Consumption
Reaching this weakness in Formidable Forms < 7.0 takes no account at all. Uncontrolled resource consumption means a request can make the server do an amount of work it never bounds, because the size or repetition of the job is taken from the request rather than capped by the code.
A single caller can hold PHP workers, database connections or disk open long enough to slow the site for everyone, without needing any account or any other flaw. For Formidable Forms the fix is 7.0: builds < 7.0 are affected, anything from 7.0 onward is not.
Remediation
Update to version 7.0, or a newer patched version
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Formidable Forms 7.0 closes this, and updating the plugin is the step that ends it.
- Firewall
- Login Security
- Alerts
External References
Related records
Other vulnerabilities in Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder
- 9.8CVE-2023-1405: Formidable Forms <= 6.1.2 PHP Object Injection
CVE-2023-1405 - 9.8CVE-2019-15780: Formidable Form Builder <= 4.02 PHP Object Injection
CVE-2019-15780 - 9.6CVE-2021-24884: Formidable Form Builder <= 4.09.04 Stored XSS
CVE-2021-24884 - 9.1Formidable Form Builder <= 2.0.21 Missing Authorization Checks
- 8.8CVE-2014-9309: Formidable Form Builder <= 1.07.11 SQL Injection
CVE-2014-9309 - 8.6Formidable Form Builder < 2.05.03 SQL Injection
- 8.3CVE-2017-20192: Formidable Form Builder < 2.05.03 Stored XSS
CVE-2017-20192 - 7.5CVE-2026-2890: Formidable… Unauthenticated Payment Integrity Bypass
CVE-2026-2890
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