CVE-2026-120534 in Advanced Custom Fields Extended PRO Plugin
Summary
by MITRE • 11/03/2026
The Advanced Custom Fields: Extended PRO plugin for WordPress is vulnerable to Limited Code Injection in all versions up to, and including, 0.9.2.6 via the render_field function. This is due to insufficient validation of form configuration parameters before merging into field settings and passing to call_user_func_array in the render_field method. This makes it possible for unauthenticated attackers to call arbitrary WordPress functions with controlled arguments. Method 1 requires the administrator to enable the non-default 'shortcode_preview' setting for the target form, while Method 2 requires the server environment to lack OpenSSL functions, causing ACF Pro's acf_decrypt to fall back to unverified base64 decoding.
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Analysis
by VulDB Data Team • 11/03/2026
The Advanced Custom Fields: Extended PRO plugin for WordPress contains a critical security vulnerability affecting all versions up to and including 0.9.2.6. This flaw manifests as a limited code injection issue within the render_field function, which is responsible for processing form configurations in the admin interface. The root cause lies in insufficient validation of user-supplied input before it is merged into field settings and subsequently passed to PHP's call_user_func_array function. Because this mechanism allows dynamic execution of functions based on provided parameters without adequate sanitization or allowlisting, attackers can manipulate these inputs to execute arbitrary WordPress core functions with controlled arguments. This represents a significant deviation from secure coding practices regarding the handling of user input in administrative contexts where privilege escalation is possible if an attacker gains access to specific configuration screens.
The vulnerability leverages two distinct exploitation methods depending on the server environment and plugin settings. The first method requires that the administrator has enabled the non-default shortcode_preview setting for a target form. This configuration choice inadvertently exposes the vulnerable code path, allowing unauthenticated attackers to inject malicious payloads into the field rendering process. By manipulating the parameters passed through this endpoint, an attacker can trick WordPress into executing functions such as eval or other dangerous operations if they are exposed via call_user_func_array. The second method exploits a cryptographic fallback mechanism within the plugin's acf_decrypt function. When the server environment lacks OpenSSL support, the decryption routine falls back to using unverified base64 decoding instead of secure encryption standards. This weakness allows attackers to craft specific inputs that bypass integrity checks, effectively enabling them to inject arbitrary code or data structures into the application logic without proper authentication or validation.
From an operational perspective, this vulnerability poses a severe risk to WordPress installations running the affected plugin versions. Although the exploitation requires either administrative configuration changes or specific server environment limitations, successful exploitation can lead to full remote code execution on the target system. Attackers could potentially compromise database integrity, steal sensitive user data, install webshells for persistent access, or use the compromised site as a pivot point for further network attacks. The impact is particularly acute because it affects unauthenticated attackers in scenarios where administrative settings are misconfigured or server environments are outdated and lack modern cryptographic libraries. This aligns with CWE-94 Improper Control of Generation of Code (Code Injection) and falls under ATT&CK technique T1059 Command and Scripting Interpreter, specifically involving dynamic code evaluation through PHP functions like call_user_func_array.
Mitigation strategies should prioritize immediate remediation by upgrading the Advanced Custom Fields: Extended PRO plugin to a version newer than 0.9.2.6 where these validation flaws have been addressed. Administrators must ensure that all plugins are kept up-to-date with security patches released by vendors. Additionally, server environments should be configured to support OpenSSL and other modern cryptographic functions to prevent fallbacks to insecure decoding methods like base64 for sensitive operations. It is also advisable to review administrative settings within the plugin to disable any non-default features such as shortcode_preview unless strictly necessary, thereby reducing the attack surface. Implementing a Web Application Firewall can provide an additional layer of defense by detecting and blocking attempts to exploit code injection patterns in HTTP requests targeting WordPress admin endpoints. Regular security audits and penetration testing should be conducted to identify similar input validation weaknesses across other plugins and custom code within the application ecosystem.