CVE-2026-73395 in Booking Calendar Plugin
Summary
by MITRE • 08/18/2026
Unauthenticated Insecure Direct Object References (IDOR) in Booking calendar, Appointment Booking System <= 3.2.36 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as an Unauthenticated Insecure Direct Object Reference within the Booking Calendar and Appointment Booking System prior to version 3.2.36 represents a critical failure in access control mechanisms that allows attackers to manipulate object identifiers directly without proper authentication or authorization checks. This flaw stems from the application's reliance on client-supplied input, such as numeric IDs passed via URL parameters or POST data, to determine which calendar events, appointments, or user-specific booking records should be retrieved and displayed. In a secure implementation, the server must validate that the authenticated user requesting access has explicit permission to view or modify the specific resource identified by the object ID. However, in vulnerable versions of this software, the system fails to perform these necessary authorization checks, effectively treating any valid identifier provided by an external actor as legitimate regardless of whether it belongs to the current session holder.
From a technical perspective, this vulnerability classifies under CWE-639, which describes Insecure Direct Object References where a reference to an internal implementation object is exposed and can be manipulated by an attacker. The operational impact is severe because it enables unauthorized access to sensitive personal data including names, contact information, appointment times, and potentially payment details associated with bookings that do not belong to the requester. Since the vulnerability is unauthenticated, there is no requirement for the attacker to possess valid credentials or even a user account on the platform. This significantly lowers the barrier to entry for exploitation, allowing any internet-connected entity to probe the system using automated scripts to enumerate valid booking IDs and extract data in bulk. The lack of authentication bypass means that traditional security controls like login walls are rendered ineffective against this specific attack vector.
The consequences of exploiting this flaw extend beyond simple privacy violations. Attackers can conduct targeted phishing campaigns by gathering detailed information about individuals who have booked appointments, such as their availability patterns or professional affiliations if stored in the booking notes. Furthermore, depending on how the application handles subsequent actions linked to these IDs, there may be a risk of unauthorized modification or deletion of bookings if similar logic flaws exist elsewhere in the codebase for update and delete operations. This aligns with MITRE ATT&CK technique T1078, specifically Valid Accounts, although in this case, no valid account is strictly required due to the unauthenticated nature of the flaw. It also relates to data exfiltration techniques where sensitive information is accessed through improper access control mechanisms rather than traditional injection or buffer overflow exploits.
Mitigation strategies must prioritize immediate patching as the primary defense vector. Administrators running versions 3.2.36 and earlier should upgrade to the latest stable release of the Booking Calendar and Appointment Booking System, which includes patches for this specific authorization logic failure. For organizations unable to update immediately due to compatibility constraints or other operational dependencies, temporary mitigation involves implementing a Web Application Firewall rule that monitors for suspicious patterns in URL parameters related to booking IDs, such as sequential integer increments often used during enumeration attacks. Additionally, developers should review the codebase to ensure that all API endpoints and page handlers enforce strict ownership verification before processing requests. This includes validating that the user ID associated with the current session matches the owner of the requested resource ID. Regular security audits focusing on access control logic are essential to prevent similar vulnerabilities from persisting in other modules of the application ecosystem.