CVE-2026-39518 Overview
CVE-2026-39518 is an Insecure Direct Object Reference (IDOR) vulnerability affecting the EventPrime event calendar management plugin for WordPress in versions up to and including 4.3.0.0. The flaw allows authenticated users holding the Subscriber role to access or manipulate objects belonging to other users by tampering with predictable identifiers in requests. The weakness maps to [CWE-639] Authorization Bypass Through User-Controlled Key. Exploitation is remote, requires low privileges, and needs no user interaction.
Critical Impact
Authenticated subscribers can bypass authorization checks and access event data belonging to other users, resulting in confidentiality exposure and partial integrity impact.
Affected Products
- EventPrime Event Calendar Management plugin for WordPress
- All versions <= 4.3.0.0
- WordPress sites with low-privilege user registration enabled
Discovery Timeline
- 2026-06-15 - CVE-2026-39518 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-39518
Vulnerability Analysis
The EventPrime plugin exposes endpoints that accept user-supplied object identifiers without verifying that the requesting account owns or has authorization to act on the referenced object. A subscriber-level account can substitute another user's resource identifier and receive data or trigger actions that should be restricted. The exploitation path is over the network, requires only valid subscriber credentials, and does not require user interaction. The disclosed impact is high for confidentiality and low for integrity, with no availability impact.
According to EPSS data dated 2026-06-18, this issue currently has a low predicted exploitation probability, but the low privilege requirement and the prevalence of open-registration WordPress sites raise practical risk.
Root Cause
The root cause is missing object-level authorization. Sensitive operations look up records by an identifier supplied in the request and return or mutate the matching record without checking the relationship between the authenticated user and the target object. This pattern is the canonical [CWE-639] weakness.
Attack Vector
An attacker registers or controls a Subscriber account on a vulnerable WordPress instance. The attacker then issues requests to EventPrime endpoints while substituting identifiers — for example, event IDs, booking IDs, or attendee references — belonging to other users. Because the backend does not enforce ownership, the server returns or modifies the targeted resource. No specialized tooling is required; standard HTTP clients and browser developer tools are sufficient.
Verified exploit code is not publicly available. See the Patchstack WordPress Vulnerability Advisory for additional technical context.
Detection Methods for CVE-2026-39518
Indicators of Compromise
- Subscriber-level accounts issuing requests to EventPrime administrative or owner-scoped endpoints.
- Sequential or enumerated numeric identifiers appearing in GET or POST parameters targeting EventPrime resources.
- Unexpected access to booking, attendee, or event records by accounts that did not create them.
- Audit log entries showing record modifications attributed to subscribers who lack edit privileges by design.
Detection Strategies
- Inspect WordPress access logs for repeated EventPrime endpoint requests that iterate object identifiers from a single low-privilege session.
- Correlate authenticated session activity with the role assigned to the WordPress user to flag privilege-context mismatches.
- Deploy a web application firewall rule that alerts on object-ID parameter tampering patterns against EventPrime URLs.
Monitoring Recommendations
- Enable verbose logging on the WordPress site and forward authentication and plugin events to a centralized logging pipeline.
- Track creation of new subscriber accounts followed by immediate activity against EventPrime endpoints.
- Review database read and write activity on EventPrime tables for access patterns spanning multiple distinct user owners from one account.
How to Mitigate CVE-2026-39518
Immediate Actions Required
- Update the EventPrime plugin to a version newer than 4.3.0.0 as soon as the vendor publishes a fix.
- Audit existing Subscriber accounts and disable accounts that show suspicious EventPrime activity.
- Temporarily disable open user registration on sites that do not require it.
Patch Information
Consult the Patchstack WordPress Vulnerability Advisory for the current patched version and update guidance. Apply the vendor-supplied patch through the WordPress plugin manager or by replacing the plugin files manually.
Workarounds
- Disable the EventPrime plugin until a fixed release is installed if event functionality is not business-critical.
- Restrict access to EventPrime endpoints at the web server or WAF layer to authenticated editors and administrators only.
- Set users_can_register to false in WordPress settings to remove the low-privilege exploitation prerequisite.
# Disable open registration via WP-CLI
wp option update users_can_register 0
# Deactivate the EventPrime plugin until patched
wp plugin deactivate eventprime-event-calendar-management
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
