CVE-2026-4807 | Appointment Booking Calendar <= 1.6.10.6 - Unauthenticated Arbitrary Appointment View, Modification and Deletion

The Appointment Booking Calendar plugin for WordPress is vulnerable to Missing Authorization in versions up to and including 1.6.10.6. This is due to a flawed authorization logic in the nonce_permissions_check() method combined with the public exposure of a site-wide reusable nonce. The plugin exposes a public_nonce value through the /wp-json/ssa/v1/embed-inner endpoint, which is accessible to unauthenticated users. The appointment deletion endpoint at /wp-json/ssa/v1/appointments/{id}/delete and /wp-json/ssa/v1/appointments/bulk use a permission check that accepts requests containing both an X-WP-Nonce header (with any arbitrary value) and an X-PUBLIC-Nonce header (with the valid public nonce). When the X-WP-Nonce validation fails, the function falls back to validating the X-PUBLIC-Nonce without properly rejecting the request. Since the public_nonce is exposed to all unauthenticated visitors and is site-wide (not user-specific or appointment-specific), attackers can obtain it and use it to view details of arbitrary appointments, including the public_edit_url, or delete arbitrary appointments by ID. This makes it possible for unauthenticated attackers to view, delete or modify any appointment in the system, disclosing sensitive appointment data, causing service disruption, and loss of booking records.

Published: 2026-05-07 Last update: 2026-05-07 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2026-4807 is rated Low Risk (26.8/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.01%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-4807

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-07 0.01%

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4807

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
3.9 2.5 [email protected]

Weakness enumeration for CVE-2026-4807

GitHub Security Advisory for CVE-2026-4807

GHSA-x96p-55v7-jmrq · Severity: medium — The Appointment Booking Calendar plugin for WordPress is vulnerable to Missing Authorization in...

Affected software / configurations for CVE-2026-4807

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-4807

URL Tags
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/booking-app-new/iframe-inner.php#L444
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-appointment-model.php#L698
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-bootstrap.php#L151
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/class-shortcodes.php#L889
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/lib/td-util/class-td-api-model.php#L110
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.9.29/includes/lib/td-util/class-td-api-model.php#L361
https://plugins.trac.wordpress.org/changeset/3511993/simply-schedule-appointments/trunk/includes
https://www.wordfence.com/threat-intel/vulnerabilities/id/436ab843-7729-4d57-9c9e-2ede2f101ddb?source=cve
cvelogic Threat Intelligence