Executive brief
The Simply Schedule Appointments plugin for WordPress, used for managing online bookings and calendars, contains a flaw that allows attackers to crash or slow down a website. By sending specific requests to the plugin, an attacker can force the server to hang, making the site unavailable to legitimate customers and staff. This could lead to lost revenue and disrupted business operations if the booking system is taken offline.
Technical details
The Simply Schedule Appointments plugin for WordPress is vulnerable to a Denial of Service (DoS) attack via the '/wp-json/ssa/v1/async' REST API endpoint. The vulnerability stems from the 'class-async-action-model.php' component, which calls the PHP sleep() function using a user-supplied delay parameter without proper rate limiting or validation. An unauthenticated remote attacker can exploit this by sending multiple requests with large delay values, effectively exhausting the server's PHP worker processes. This resource exhaustion prevents the web server from processing legitimate requests. The issue affects all versions up to and including 1.6.11.5.
Affected products
- Simply Schedule Appointments Simply Schedule Appointments Booking Plugin Up to, and including, 1.6.11.5
Timeline
- 2026-05-27: advisory: NVD publication date