CVE-2026-103304 Overview
CVE-2026-103304 affects the eaSYNC Booking WordPress plugin in versions prior to 1.3.31. The plugin fails to perform authorization or nonce checks on several cancellation-related AJAX actions. Unauthenticated attackers can abuse these endpoints to create booking cancellation requests, trigger booking notification emails, and overwrite the content of outbound emails sent by the site.
The weakness is classified under CWE-862: Missing Authorization. The flaw does not require authentication, user interaction, or elevated privileges. Attackers reach it over the network through standard WordPress AJAX endpoints exposed by the plugin.
Critical Impact
Unauthenticated attackers can tamper with booking workflows and hijack notification email content, enabling spam, phishing, and operational disruption of affected WordPress sites.
Affected Products
- eaSYNC Booking WordPress plugin versions prior to 1.3.31
- WordPress sites with the eaSYNC Booking plugin enabled
- Any booking workflow dependent on the plugin's cancellation AJAX actions
Discovery Timeline
- 2026-10-15 - CVE-2026-103304 published to NVD
- 2026-10-15 - Last updated in NVD database
Technical Details for CVE-2026-103304
Vulnerability Analysis
The eaSYNC Booking plugin registers several AJAX actions responsible for handling booking cancellation flows. These handlers do not validate the identity of the caller and do not enforce WordPress nonce verification. As a result, requests originating from unauthenticated clients are processed as if they were legitimate administrative or user-initiated actions.
Three distinct abuse paths exist. First, an attacker can submit arbitrary booking cancellation requests against any booking record exposed by the plugin. Second, an attacker can repeatedly trigger booking notification emails, enabling spam campaigns originating from the victim's domain. Third, an attacker can overwrite the stored content of notification emails that the site subsequently sends to legitimate recipients.
The third behavior is the most consequential. By rewriting notification email bodies, an attacker can insert phishing content, malicious links, or fraudulent instructions into messages that recipients trust because they originate from the site's legitimate mail infrastructure.
Root Cause
The root cause is a missing authorization check [CWE-862] combined with the absence of a check_ajax_referer() or wp_verify_nonce() call in multiple cancellation-related AJAX handlers. WordPress exposes AJAX endpoints through admin-ajax.php, including a wp_ajax_nopriv_ variant for unauthenticated users. The plugin registers cancellation actions on this unauthenticated hook without any gating logic.
Attack Vector
Exploitation requires only HTTP access to the target WordPress site. An attacker issues crafted POST requests to wp-admin/admin-ajax.php with the vulnerable action parameter and the booking identifiers or email payload to be injected. No credentials, session, or user interaction are required. See the WPScan Vulnerability Report for technical details on the affected handlers.
Detect Identity Attacks the Moment Authentication Fails
Singularity™ Identity surfaces credential misuse, lateral movement, and privilege escalation in real time, so you can contain the breach before it spreads.
Stop Identity AttacksDetection Methods for CVE-2026-103304
Indicators of Compromise
- Unexpected POST requests to /wp-admin/admin-ajax.php referencing eaSYNC cancellation actions from unauthenticated sources
- Unexplained changes to booking notification email templates stored in the WordPress database
- Bursts of outbound booking notification emails without corresponding legitimate booking activity
- Customer reports of cancellation notifications they did not request
Detection Strategies
- Review web server access logs for anomalous volumes of requests to admin-ajax.php with eaSYNC-related action parameter values
- Monitor the WordPress options and plugin tables for unauthorized modifications to email template content
- Correlate spikes in outbound SMTP activity with the absence of corresponding authenticated administrative sessions
Monitoring Recommendations
- Enable WordPress audit logging to capture plugin option changes and AJAX action invocations
- Forward web server and WordPress logs to a centralized analytics platform for anomaly detection on admin-ajax.php traffic
- Alert on outbound mail volume thresholds that exceed baseline booking activity
How to Mitigate CVE-2026-103304
Immediate Actions Required
- Update the eaSYNC Booking plugin to version 1.3.31 or later on all affected WordPress installations
- Audit stored email templates and booking records for unauthorized modifications prior to the upgrade
- Rotate any transactional email credentials if abuse of outbound mail is suspected
Patch Information
The vendor has addressed the issue in eaSYNC Booking version 1.3.31. The fix introduces authorization and nonce verification on the previously unprotected cancellation AJAX actions. Site operators should apply the update through the WordPress plugin manager or via WP-CLI. Refer to the WPScan Vulnerability Report for advisory details.
Workarounds
- Restrict access to /wp-admin/admin-ajax.php from untrusted networks using a web application firewall rule
- Block requests to admin-ajax.php where the action parameter matches the vulnerable eaSYNC cancellation handlers until the patch is applied
- Disable the eaSYNC Booking plugin if an immediate upgrade is not feasible
# Update the plugin using WP-CLI
wp plugin update easync-booking --version=1.3.31
wp plugin list --name=easync-booking --fields=name,status,version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
