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Booking Calendar <= 11.8.4 — Unauthenticated Duplicate Slot Booking

CVE-2026-39601Published · Updated

Action summary

Affected: ≤11.8.4Update to 11.9 or newer

All remediation steps
Watch plugin
Severity
Medium5.3
CVSS
5.3
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:N User interaction
None
S:U Scope
Unchanged
C:N Confidentiality
None
I:L Integrity
Low
A:N Availability
None
Weakness
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
Required access
No account needed
Exploit prediction (EPSS)
0.2% chance in 30 days4th percentile
CISA KEV
Not listed
On this page8

Am I affected?

Booking Calendar booking

  1. Affected≤ 11.8.4
  2. Patched in11.9

Update to 11.9 or newer.

You are affected if you run ≤ 11.8.4. Version 11.9 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Booking Calendar.
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 11.9, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch Booking Calendar to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to Ananda Dhakal.

The Booking Calendar plugin for WordPress is vulnerable to Race Condition in all versions up to, and including, 11.8.4. This is due to missing real-time date-availability validation at the moment of date selection, allowing a date shown as available during calendar load to be selected and submitted after a concurrent booking had taken it. This makes it possible for unauthenticated attackers to make duplicate bookings for the same resource slot by exploiting the window between calendar availability display and actual booking submission.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in Booking Calendar

All 38
More vulnerabilities in Booking Calendar
SeverityVulnerabilityCVEPublished
Medium5.3Unauthenticated Sensitive Information Exposure in 'WPBC_FLEXTIMELINE_NAV' AJAX Action
≤11.4.3Update to 11.5
CVE-2026-18496
Low2.711.8.2 - Authenticated (Editor+) Information Exposure
10.15 – 11.8.2Update to 11.8.3
CVE-2026-105195
Medium5.3Unauthenticated Information Exposure
<11.8Update to 11.8
CVE-2026-105193
Medium6.1Reflected Cross-Site Scripting via 'wpbc_auto_fill' Parameter
≤11.8.3Update to 11.8.4
CVE-2026-93655
Medium6.1Reflected Cross-Site Scripting via 'options' Parameter
≤11.8.2Update to 11.8.3
CVE-2026-92561

Timeline

  1. CVE published

    Severity medium, CVSS 5.3

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
CVE® identifiers
Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
EPSS
Exploit Prediction Scoring System by FIRST.org.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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