CVE-2026-4021 Auth bypass in Contest Gallery – Upload & Vote Photos, Media, Sell with PayPal & Stripe
Unauthenticated attackers can take over admin accounts via type confusion in email confirmation when optional registration settings are enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-4021?
CVE-2026-4021 is a high-severity authentication bypass vulnerability in contest-gallery Contest Gallery – Upload & Vote Photos, Media, Sell with PayPal & Stripe, published on 23 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-287
Which versions are affected by CVE-2026-4021?
How do I fix CVE-2026-4021?
No fix has been published for CVE-2026-4021 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-4021 being exploited?
There is no known exploitation of CVE-2026-4021 in the wild and no public exploit code.
Sources
Also known as GHSA-m4rm-grq4-j8wp.