CVE-2026-4121

CVE-2026-4121 is a medium-severity vulnerability with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-352.

Key facts

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.

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.
How severe is CVE-2026-4121?
CVE-2026-4121 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-4121 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-4121?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-4121 have an EU (EUVD) identifier?
Yes. CVE-2026-4121 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24664.
When was CVE-2026-4121 published?
CVE-2026-4121 was published on 2026-04-22 and last updated on 2026-06-17.

References

Other CWE-352 (Cross-Site Request Forgery (CSRF)) vulnerabilities

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