CVE-2026-103347

hCaptcha for WP <= 5.3.0 - Unauthenticated Captcha Verification Bypass

2026-10-01 00:00

Strategic Overview

Status: Patched in 5.4.0
Affected Plugin: hCaptcha for WP
Affected Version: <= 5.3.0
CVSS: 7.3High
Weakness type: CWE-804 · Guessable CAPTCHA
CVE: CVE-2026-103347

View all hCaptcha for WP vulnerabilities

At a glance

CVE-2026-103347 is a high-severity Guessable CAPTCHA vulnerability in the hCaptcha for WP WordPress plugin, affecting versions <= 5.3.0. It carries a CVSS score of 7.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 5.4.0; sites on affected versions should update now. Disclosed October 2026, reported by bamper1.

Vulnerability Overview

The hCaptcha for WP plugin for WordPress is vulnerable to Bypass Vulnerability in all versions up to, and including, 5.3.0. This is due to form action registrations stored exclusively in a WordPress transient that could expire or be evicted, causing get_registered_form() to return null and skip the hCaptcha requirement for auto-verified forms. This makes it possible for unauthenticated attackers to bypass hCaptcha verification on auto-verified forms by waiting for or triggering transient expiration, causing the plugin to skip the captcha check entirely. The site must use AutoVerify (auto-detected hCaptcha integration) for at least one form.

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.

CWE-804: Guessable CAPTCHA

The product uses a CAPTCHA challenge, but the challenge can be guessed or automatically recognized by a non-human actor.

Remediation

Update to version 5.4.0, or a newer patched version

How does WordSec protect against this?

This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: hCaptcha for WP 5.4.0 closes this, and updating the plugin is the step that ends it.

Login Security
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-103347 https://www.wordfence.com/threat-intel/vulnerabilities/id/dd3aa31d-58ba-4634-b0e2-b2b4339cb191 https://nvd.nist.gov/vuln/detail/CVE-2026-103347

Related records

Other vulnerabilities in hCaptcha for WP

CVSS Vector

7.3

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityLow
IntegrityLow
AvailabilityLow

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