CVE-2026-11426 in Under Construction Page Plugin
Summary
by MITRE • 07/11/2026
The UnderConstructionPage PRO plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 5.76. This is due to the plugin accepting arbitrary local file paths in the template_thumbnail parameter and copying their contents into a publicly accessible uploads file. This makes it possible for authenticated attackers, with Subscriber-level access and above, to read arbitrary files on the server, which can contain sensitive information.
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Analysis
by VulDB Data Team • 07/11/2026
The UnderConstructionPage PRO plugin for WordPress presents a critical arbitrary file read vulnerability affecting all versions up to and including 5.76. This security flaw resides in the plugin's handling of the template_thumbnail parameter which accepts arbitrary local file paths without proper validation or sanitization. The vulnerability allows authenticated attackers with subscriber-level privileges or higher to exploit this weakness by submitting malicious file paths that are then copied into publicly accessible upload directories, effectively exposing sensitive server files to unauthorized access.
This vulnerability represents a classic path traversal and privilege escalation issue that aligns with CWE-22 - Improper Limitation of a Pathname to a Restricted Directory. The flaw enables attackers to bypass normal file system access controls by leveraging the plugin's legitimate file handling mechanisms to read files that should remain protected. The attack vector is particularly concerning because it requires only subscriber-level authentication, which is often easily obtainable through social engineering or credential compromise attacks, making the vulnerability accessible to a broad range of threat actors.
The operational impact of this vulnerability extends beyond simple information disclosure as the exposed files may contain database credentials, configuration details, user data, application secrets, and other sensitive materials that could be leveraged for further attacks. The publicly accessible nature of the copied files means that once an attacker successfully exploits this vulnerability, they can immediately access and exfiltrate potentially critical information without requiring additional attack vectors or elevated privileges.
From a defensive perspective, organizations should immediately update to the latest version of the UnderConstructionPage PRO plugin where this vulnerability has been addressed. The mitigation strategy should also include monitoring for suspicious file uploads in the WordPress uploads directory and implementing proper input validation for all user-supplied parameters. Additionally, network segmentation and access control measures can help limit the potential impact if an attacker successfully exploits this vulnerability, while following ATT&CK framework guidance on privilege escalation and credential access techniques can aid in detecting and responding to such attacks.
The vulnerability demonstrates the importance of proper parameter validation and secure file handling practices in web applications. The plugin's failure to implement adequate checks on the template_thumbnail parameter represents a fundamental security oversight that could have been prevented through proper input sanitization, file path validation, and adherence to secure coding practices. Organizations should conduct comprehensive security assessments of their WordPress installations to identify similar vulnerabilities in other plugins or themes that might be susceptible to similar arbitrary file read attacks.