Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin: A security weakness
Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin is affected by a security weakness. The vulnerable path is reachable without authentication. The resulting impact depends on how the affected component exposes the vulnerable operation. The published affected range is <= 1.6.11.5.
- Component
- Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin
- Plugin slug
simply-schedule-appointments- Affected
- <= 1.6.11.5
- Safe version
> 1.6.11.5- Published
- May 27, 2026
This CVE was published May 27, 2026 and is one of 31 known issues for this plugin.
Update, patch or deactivate.
Update Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin to a release after 1.6.11.5, or disable and remove it until a fixed version is available.
A safe version is available, so updating to that version or later is the preferred remediation. If an immediate update is not practical, consider a targeted application patch or temporarily restricting the affected functionality.
Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.
Technical description
The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to denial of service in all versions up to, and including, 1.6.11.5. This is due to a publicly accessible REST API endpoint (/wp-json/ssa/v1/async) that calls PHP's sleep() function on a user-supplied delay parameter without any rate limiting. This makes it possible for unauthenticated attackers to exhaust PHP worker processes, denying access to the site to legitimate users.
CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L