Is CVE-2026-4021 actively exploited?

No active exploitation of CVE-2026-4021 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-4021 be exploited remotely?

Yes. CVE-2026-4021 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-4021?

CVE-2026-4021 has a CVSS score of 8.1 (HIGH).

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HIGH

CVE-2026-4021

CWE-287Published: March 24, 2026· Updated: Mar 24, 2026

8.1

CVSS v3.1

EPSS:0.12%probability of exploitation in 30 daysPercentile:30.8th

Official Description

The Contest Gallery plugin for WordPress is vulnerable to an authentication bypass leading to admin account takeover in all versions up to, and including, 28.1.5. This is due to the email confirmation handler in `users-registry-check-after-email-or-pin-confirmation.php` using the user's email string in a `WHERE ID = %s` clause instead of the numeric user ID, combined with an unauthenticated key-based login endpoint in `ajax-functions-frontend.php`. When the non-default `RegMailOptional=1` setting is enabled, an attacker can register with a crafted email starting with the target user ID (e.g., `[email protected]`), trigger the confirmation flow to overwrite the admin's `user_activation_key` via MySQL integer coercion, and then use the `post_cg1l_login_user_by_key` AJAX action to authenticate as the admin without any credentials. This makes it possible for unauthenticated attackers to take over any WordPress administrator account and gain full site control.

NVD Source

Technical Analysis

CVE-2026-4021 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.1.

From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.