CVE-2026-73395: Booking Calendar IDOR Vulnerability

CVE-2026-73395 Overview

CVE-2026-73395 is an unauthenticated Insecure Direct Object References (IDOR) vulnerability affecting the WordPress plugin Booking calendar, Appointment Booking System in versions up to and including 3.2.36. The flaw allows remote attackers to reference booking objects belonging to other users without authentication. Successful exploitation can lead to unauthorized access, modification, or manipulation of appointment records stored by the plugin. The vulnerability is tracked under CWE-639: Authorization Bypass Through User-Controlled Key.

Critical Impact
Unauthenticated attackers can access or tamper with booking records belonging to other users, exposing appointment data and disrupting scheduling integrity on affected WordPress sites.

Affected Products

WordPress plugin Booking calendar, Appointment Booking System
All versions up to and including 3.2.36
WordPress sites running the vulnerable plugin without applied patches

Discovery Timeline

2026-08-18 - CVE-2026-73395 published to NVD
2026-08-20 - Last updated in NVD database

Technical Details for CVE-2026-73395

Vulnerability Analysis

The vulnerability resides in the plugin's handling of direct object references for booking records. The plugin exposes endpoints that accept object identifiers, such as booking IDs, without verifying whether the requester owns or has authorization to access the referenced resource. An unauthenticated attacker can iterate or guess identifiers to interact with records belonging to other users.

This flaw is classified as CWE-639, where authorization decisions rely on user-controlled input rather than server-side ownership checks. The impact scope covers integrity and availability of booking data, while confidentiality impact is limited according to the published CVSS metrics.

Detailed exploitation mechanics are documented in the Patchstack Vulnerability Report.

Root Cause

The root cause is missing authorization checks on booking-related actions. The plugin trusts identifiers supplied in requests without validating that the caller has a legitimate relationship to the referenced booking. No session, capability, or ownership verification is enforced before performing the requested action.

Attack Vector

Exploitation occurs over the network without authentication or user interaction. An attacker sends crafted HTTP requests to the plugin's endpoints, substituting booking identifiers to reach records that should be inaccessible. Because the attack requires only knowledge or enumeration of numeric identifiers, automated scripts can systematically target victim sites.

No verified public exploit code is available at this time. Refer to the Patchstack advisory for technical details.

Detection Methods for CVE-2026-73395

Indicators of Compromise

Unexpected modifications to booking records without corresponding authenticated user sessions in WordPress logs
Sequential or enumerated booking_id values appearing in web server access logs from a single source IP
Anomalous HTTP requests to plugin endpoints from unauthenticated clients targeting booking-related actions

Detection Strategies

Inspect web server and WordPress logs for requests to Booking calendar plugin endpoints that lack an authenticated session cookie
Correlate booking record changes with authentication events to identify state changes performed without a valid user context
Deploy web application firewall rules to flag ID enumeration patterns targeting the plugin's action handlers

Monitoring Recommendations

Enable verbose logging on the WordPress instance to capture request parameters and originating IP addresses
Alert on high-volume requests to plugin endpoints containing incrementing numeric parameters
Review booking database tables for unexpected deletions, modifications, or status changes on a scheduled basis

How to Mitigate CVE-2026-73395

Immediate Actions Required

Update the Booking calendar, Appointment Booking System plugin to a version newer than 3.2.36 once the vendor publishes a fixed release
Restrict access to WordPress admin and plugin endpoints using IP allowlisting or authentication proxies where feasible
Audit existing booking records for signs of unauthorized modification

Patch Information

Refer to the Patchstack Vulnerability Report for the latest fix status and vendor-supplied patched version. Site administrators should subscribe to plugin update notifications and apply patches promptly.

Workarounds

Deploy a web application firewall rule to block unauthenticated requests to plugin endpoints that reference booking identifiers
Temporarily disable the Booking calendar, Appointment Booking System plugin if a patched version is not yet available and business operations permit
Enforce authentication requirements at the reverse proxy layer for all plugin action URLs

bash

# Example nginx rule to block unauthenticated access to plugin endpoints
location ~* /wp-content/plugins/booking-calendar/ {
    if ($http_cookie !~* "wordpress_logged_in") {
        return 403;
    }
}