CVE-2026-39537 Overview
CVE-2026-39537 is an unauthenticated Local File Inclusion (LFI) vulnerability affecting the Mikado Core WordPress plugin in versions up to and including 1.6. The flaw maps to CWE-98, improper control of filename for include/require statement in PHP programs. An unauthenticated remote attacker can supply attacker-controlled input that is passed to a PHP file inclusion function, causing the server to load arbitrary local files. Successful exploitation can disclose sensitive configuration data, expose credentials, and lead to code execution when combined with file upload primitives or log poisoning techniques.
Critical Impact
Unauthenticated attackers can include arbitrary local files on the target WordPress server, exposing secrets and potentially enabling remote code execution.
Affected Products
- Mikado Core WordPress plugin versions <= 1.6
- WordPress sites that have the Mikado Core plugin installed and activated
- Themes from the Mikado-Themes ecosystem that bundle the Mikado Core plugin
Discovery Timeline
- 2026-06-17 - CVE-2026-39537 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-39537
Vulnerability Analysis
The vulnerability is classified as an unauthenticated Local File Inclusion in the Mikado Core plugin. LFI flaws of this class allow an attacker to influence the path argument passed to PHP file inclusion functions such as include, require, include_once, or require_once. Because the request requires no authentication, any remote user who can reach the WordPress site can trigger the vulnerable code path.
When an attacker controls the included file path, they can read PHP source files, environment files, and configuration data on the server. Reading wp-config.php exposes database credentials and authentication keys, which attackers reuse to pivot deeper into the environment.
The attack complexity is rated High, which indicates that exploitation may require specific conditions such as a particular plugin configuration, environment settings, or timing. Successful exploitation impacts confidentiality, integrity, and availability.
Root Cause
The root cause is improper validation and sanitization of user-supplied input that is used to construct a filename in a PHP inclusion statement. The plugin accepts request parameters and passes them into an include path without enforcing an allowlist of permitted files or normalizing path traversal sequences such as ../. This matches the CWE-98 pattern.
Attack Vector
The attack vector is Network. An attacker sends a crafted HTTP request to a vulnerable endpoint exposed by the Mikado Core plugin. The request includes a parameter whose value points to a local file path. The plugin includes the file, executing any PHP code it contains or returning its contents in the response. Attackers commonly chain LFI with log poisoning, session file inclusion, or PHP wrappers such as php://filter to escalate impact toward code execution.
No verified public proof-of-concept code was available at the time of publication. Refer to the Patchstack Mikado Core Vulnerability advisory for additional technical details.
Detection Methods for CVE-2026-39537
Indicators of Compromise
- HTTP requests to Mikado Core plugin endpoints that contain path traversal sequences such as ../../, encoded variants like %2e%2e%2f, or PHP stream wrappers such as php://filter and php://input
- Web server access logs showing requests to plugin parameters with values referencing sensitive files like wp-config.php, /etc/passwd, or proc/self/environ
- Unexpected outbound connections or new administrative user creation following anomalous requests to plugin URLs
Detection Strategies
- Inspect WordPress and web server logs for requests targeting the Mikado Core plugin with suspicious file path parameters
- Deploy web application firewall rules that match LFI signatures, including directory traversal sequences and PHP wrapper schemes
- Correlate PHP error logs with HTTP request logs to identify failed inclusion attempts that precede successful exploitation
Monitoring Recommendations
- Alert on reads of sensitive files such as wp-config.php from the web server process when the originating request hits a plugin endpoint
- Monitor file integrity on the WordPress installation, especially the wp-content/plugins/mikado-core/ directory, for unexpected modifications
- Track creation of new administrative WordPress accounts and changes to authentication keys, which often follow credential disclosure via LFI
How to Mitigate CVE-2026-39537
Immediate Actions Required
- Identify all WordPress installations running Mikado Core <= 1.6 and prioritize them for patching
- Restrict access to the WordPress site at the network layer or behind a web application firewall while a fix is applied
- Rotate WordPress salts, database credentials, and any secrets readable from the web root, since unauthenticated LFI may have already exposed them
Patch Information
Review the Patchstack Mikado Core Vulnerability advisory for vendor remediation guidance. Upgrade Mikado Core to a version above 1.6 once the vendor releases a fixed build. If no patched version is available, consider deactivating and removing the plugin until a fix is published.
Workarounds
- Deactivate the Mikado Core plugin until a patched release is installed
- Apply virtual patching through a WordPress-aware web application firewall that blocks path traversal and PHP wrapper payloads against plugin endpoints
- Harden PHP by setting open_basedir to restrict file inclusion to the WordPress installation directory and disable allow_url_include
# Example PHP hardening in php.ini to limit LFI blast radius
open_basedir = "/var/www/html/:/tmp/"
allow_url_include = Off
allow_url_fopen = Off
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
