CVE-2026-4121

Description

The Kcaptcha plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to and including 1.0.1. This is due to missing nonce validation in the plugin's settings page handler (admin/setting.php). The settings form does not include a wp_nonce_field() and the form processing code does not call wp_verify_nonce() or check_admin_referer() before saving settings to the database via $wpdb->update(). This makes it possible for unauthenticated attackers to modify the plugin's CAPTCHA settings (enabling or disabling CAPTCHA on login, registration, lost password, and comment forms) via a forged request, granted they can trick a site administrator into performing an action such as clicking a link.

CVSS v3.1 Score

4.3

MEDIUM

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

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.00%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-352 Cross-Site Request Forgery

References

Other References

https://plugins.trac.wordpress.org/browser/kcaptcha/tags/1.0.1/admin/setting.php#L12 https://plugins.trac.wordpress.org/browser/kcaptcha/tags/1.0.1/admin/setting.php#L30 https://plugins.trac.wordpress.org/browser/kcaptcha/tags/1.0.1/admin/setting.php#L47 https://plugins.trac.wordpress.org/browser/kcaptcha/trunk/admin/setting.php#L12 https://plugins.trac.wordpress.org/browser/kcaptcha/trunk/admin/setting.php#L30 https://plugins.trac.wordpress.org/browser/kcaptcha/trunk/admin/setting.php#L47 https://www.wordfence.com/threat-intel/vulnerabilities/id/a6c1c73b-76e3-4cb9-ad53-9d5d4e7519c9?source=cve

Frequently Asked Questions

What is CVE-2026-4121? +

The Kcaptcha plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to and including 1.0.1. This is due to missing nonce validation in the plugin's settings page handler (admin/setting.php). The settings form does not include a wp_nonce_field() and the form processing code does not call wp_verify_nonce() or check_admin_referer() before saving settings to the database via $wpdb->update(). This makes it possible for unauthenticated attackers to modify the plugin's CAPTCHA settings (enabling or disabling CAPTCHA on login, registration, lost password, and comment forms) via a forged request, granted they can trick a site administrator into performing an action such as clicking a link. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-4121? +

CVE-2026-4121 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-4121? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-35220

Lack of CSRF token validation lead to a CSRF attack vector in the admin activation endpoint of com_users.

CVE-2026-40325

Masa CMS is a content management system forked from Mura CMS. In versions 7.5.2 and earlier, the `cTrash.restore` function does …

CVE-2026-40174

Masa CMS is a content management system forked from Mura CMS. In versions 7.5.2 and earlier, the cUsers.updateAddress function does …

CVE-2024-6662

Websites managed by MegaBIP in versions below 5.15 are vulnerable to Cross-Site Request Forgery (CSRF) as the form available under …

CVE-2026-42286

Emlog is an open source website building system. Prior to version 2.6.11, missing CSRF protection in critical admin functions allows …

CVE-2024-7141

Versions of Gliffy Online prior to versions 4.14.0-7 contains a Cross Site Request Forgery (CSRF) flaw.