Description

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in WPdevelop Booking Calendar booking allows Leveraging Race Conditions.This issue affects Booking Calendar: from n/a through 11.8.4.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.7",
  "pubDate": "2026-10-02T15:17:09.907Z",
  "pubdate": "2026-10-02T15:17:09.907Z",
  "executiveSummary": "A concurrent execution vulnerability involving improper synchronization of shared resources—specifically a race condition—has been identified within the WPdevelop Booking Calendar plugin for WordPress. This security flaw affects the application's booking functionality across versions ranging from n/a up to and including 11.8.4. The core of the vulnerability resides in the application's failure to serialize concurrent operations that access and modify shared booking records. Consequently, remote attackers can exploit this specific timing window to execute multiple simultaneous requests, allowing them to leverage race conditions. This exploitation can result in the subversion of transactional business logic, unauthorized modifications of booking states, resource exhaustion, or double-booking exploits.\nThe risk implications are significant for platforms relying on the integrity of scheduling data, as attackers can bypass validation checks that would normally restrict simultaneous modifications. To exploit this vulnerability, an attacker must generate highly synchronized network traffic directed at vulnerable transactional endpoints. Administrators should immediately apply available updates to mitigate the risk of state corruption and unauthorized resource manipulation.",
  "technicalDetails": "The underlying security weakness in the WPdevelop Booking Calendar plugin (affecting versions n/a through 11.8.4) is classified under CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'). In highly concurrent web server environments, multiple PHP processes or threads execute incoming HTTP requests in parallel. When handling critical transactional operations, such as creating, updating, or validating a booking, the application must read the current state from a shared database, verify availability constraints, and write the updated state back to the database.\nThe vulnerability arises because the plugin's booking handling component lacks adequate synchronization controls or atomic execution blocks. When a user initiates a booking, the system performs a validation step (a 'check' phase) to ensure the requested slot is available, followed by a state update (a 'write' phase). Without proper transaction isolation or mutual exclusion primitives, a significant race window exists between the check phase and the write phase.\nExploitation of this vulnerability typically follows a structured workflow. First, an attacker identifies a high-value booking transaction endpoint within the WPdevelop Booking Calendar plugin. Next, the attacker crafts multiple identical HTTP requests designed to book or alter the same specific resource or slot. Using specialized automated tools or scripts capable of HTTP/2 multiplexing, these requests are transmitted in parallel to ensure near-simultaneous arrival at the target web server.\nThe backend server receives these requests concurrently and spawns parallel execution threads. Thread A and Thread B both enter the validation phase at the exact same moment. Because Thread A has not yet committed its state update to the database, Thread B reads the pre-existing state. Both threads find the target slot available and validate successfully. Finally, both threads proceed to write their changes, allowing the attacker to execute overlapping transactions, bypass scheduling constraints, or potentially overwrite critical booking parameters.\nBy successfully leveraging this race condition, attackers can disrupt the operational integrity of the booking system. This can lead to unauthorized slot allocations, evasion of reservation rules, or inconsistencies in transactional state records, undermining trust in the application's state-management engine."
}