CVE-2026-111311 in DoubleScale CRM All-in-One CRM Plugin
Summary
by MITRE • 10/16/2026
The DoubleScale | All-in-One CRM – Sales, Multi-Channel Marketing, Newsletter, Booking, Helpdesk, Automation, MCP & More plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 1.5.1 via the store_upload function. This is due to a fail-open extension allow-list in extension_is_allowed() that returns true when wp_check_filetype() yields an empty type for unrecognized extensions such as .php, combined with magic-byte-only MIME detection and no capability check beyond is_user_logged_in(). This makes it possible for authenticated attackers, with subscriber-level access and above, to upload files that may be executable, which makes remote code execution possible. Exploitation requires the Helpdesk module to be enabled, as the vulnerable REST endpoint is only registered when that module is active.
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Analysis
by VulDB Data Team • 10/16/2026
The DoubleScale All-in-One CRM plugin for WordPress contains a critical Arbitrary File Upload vulnerability affecting all versions up to and including 1.5.1. This flaw resides within the store_upload function, which processes file uploads through an extension allow-list mechanism implemented in the extension_is_allowed helper function. The core technical failure stems from how this function handles unrecognized file extensions. Specifically, when wp_check_filetype() fails to identify a valid MIME type for a given extension, such as .php, it returns an empty string. Due to a fail-open logic error, the extension_is_allowed function interprets this empty result as true, effectively bypassing the intended restriction on executable file types. This design flaw allows attackers to upload files with dangerous extensions that would normally be blocked by standard WordPress security filters.
The severity of this vulnerability is compounded by additional weaknesses in input validation and access control. The plugin relies primarily on magic-byte-only MIME detection for further verification, which can often be bypassed or manipulated depending on the file content. More critically, the only capability check performed before allowing the upload is a basic authentication check via is_user_logged_in(). This means that any authenticated user with subscriber-level access and above can exploit this flaw. In many WordPress installations, subscribers are low-privilege users who should not have the ability to modify site files or execute code. The lack of stricter capability checks allows these lower-tier accounts to upload arbitrary scripts to the server.
Exploitation of this vulnerability leads directly to Remote Code Execution on the affected system. Once an attacker successfully uploads a malicious PHP file, they can trigger its execution by accessing it through the web server. This grants the attacker full control over the WordPress installation and potentially the underlying host environment, depending on the permissions of the web server process. The operational impact is severe, as it allows for data theft, defacement, malware distribution, or using the compromised site as a pivot point for further attacks against internal networks. It effectively undermines the integrity and confidentiality guarantees provided by the CMS platform.
It is important to note that exploitation requires specific conditions within the target environment. The vulnerable REST endpoint responsible for handling these uploads is only registered when the Helpdesk module of the DoubleScale plugin is enabled. If this module is inactive, the attack vector remains inaccessible regardless of other vulnerabilities present in the codebase. This dependency means that administrators who do not utilize the Helpdesk feature may be less exposed to this specific threat, although they should still update their plugins as a matter of general security hygiene.
To mitigate this risk, immediate action is required from site administrators and developers. The primary remediation step is to upgrade the DoubleScale All-in-One CRM plugin to version 1.5.2 or later, where these issues have been addressed by implementing stricter file type validation and correcting the logic in extension_is_allowed(). Administrators should also ensure that only trusted users are granted subscriber-level access or higher privileges within WordPress. Implementing Web Application Firewalls can provide an additional layer of defense by blocking requests containing suspicious file uploads before they reach the application code. Regular security audits and adherence to secure coding standards, such as those outlined in CWE-434 for Unrestricted Upload of File with Dangerous Type, are essential for preventing similar vulnerabilities in future development cycles.