CVE-2024-13821 Overview
CVE-2024-13821 affects the WP Booking Calendar plugin for WordPress in all versions up to and including 10.10. The plugin fails to require re-verification when a booking is modified after confirmation. Unauthenticated attackers can manipulate approved bookings over the network without any user interaction. The weakness is classified as improper authorization [CWE-285] and impacts the integrity of booking records. Confidentiality and availability are not directly affected, but tampered reservations can disrupt business operations that rely on the plugin for scheduling.
Critical Impact
Unauthenticated attackers can modify confirmed bookings in WP Booking Calendar through 10.10, undermining the integrity of reservation data.
Affected Products
- WP Booking Calendar plugin for WordPress — all versions through 10.10
- Vendor: wpbookingcalendar
- Component: wpbookingcalendar:booking_calendar
Discovery Timeline
- 2025-02-12 - CVE-2024-13821 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-13821
Vulnerability Analysis
The WP Booking Calendar plugin exposes booking modification endpoints that treat the initial booking token as a sufficient trust anchor. After a booking is approved, the plugin accepts subsequent change requests without re-authenticating or re-verifying the requester. An attacker who can reach the WordPress site over the network can issue crafted modification requests against existing bookings. Because no authentication is required, exploitation does not depend on account access or social engineering. The flaw is a business logic failure in the post-confirmation workflow rather than a memory-safety or injection defect.
Root Cause
The root cause is missing authorization enforcement on booking-change actions after confirmation. The plugin does not re-validate ownership, re-check a one-time token, or require administrator approval for post-confirmation edits. This matches the pattern described by CWE-285: Improper Authorization, where an action is permitted without an adequate authorization check.
Attack Vector
Exploitation occurs remotely over HTTP(S) against any WordPress site running a vulnerable version of the plugin. An attacker enumerates or guesses booking identifiers, then submits modification requests to the plugin's booking endpoints. Because re-verification is absent, the server accepts the changes and updates the confirmed reservation. No credentials, administrative access, or user interaction are required. Public technical analysis is available in the Wordfence Vulnerability Report and the fix is visible in the WordPress Plugin Changeset.
No verified public exploit code is available. The vulnerability mechanism is described in prose only.
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Stop Identity AttacksDetection Methods for CVE-2024-13821
Indicators of Compromise
- Unexpected modifications to previously confirmed bookings in the plugin database tables.
- POST requests to WP Booking Calendar AJAX endpoints originating from IPs that never completed the original booking flow.
- Booking records whose modification timestamp is later than the approval timestamp without a corresponding administrator session.
- Anomalous sequences of booking enumeration requests followed by edit requests.
Detection Strategies
- Enable WordPress and web server access logging and alert on repeated requests to admin-ajax.php carrying WP Booking Calendar action parameters from unauthenticated sessions.
- Compare current booking state against periodic database snapshots to surface silent edits.
- Deploy a web application firewall rule that inspects booking modification parameters and challenges unauthenticated callers.
Monitoring Recommendations
- Centralize WordPress audit logs and plugin activity in a SIEM for correlation across sites.
- Monitor the WP Booking Calendar plugin version across managed WordPress fleets and flag any instance at or below 10.10.
- Track outbound notification emails for cancellation or change confirmations that customers did not initiate.
How to Mitigate CVE-2024-13821
Immediate Actions Required
- Update WP Booking Calendar to a version later than 10.10 that includes the fix referenced in the vendor changeset.
- Audit recent booking modifications for unauthorized changes and notify affected customers where appropriate.
- Restrict access to the WordPress site with a WAF rule blocking unauthenticated calls to booking modification endpoints until patched.
Patch Information
The vendor addressed the issue in the WordPress plugin repository. Review the WordPress Plugin Changeset for the committed fix and upgrade to the patched release through the WordPress admin plugin updater.
Workarounds
- Temporarily disable the WP Booking Calendar plugin on sites that cannot be updated immediately.
- Place booking modification endpoints behind an authentication gateway or IP allowlist.
- Require manual administrator approval for any booking change event through a reverse-proxy or WAF rule.
# Example WP-CLI commands to inventory and update the plugin
wp plugin get booking --field=version
wp plugin update booking
wp plugin deactivate booking # fallback if a patched version is unavailable
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
