CVE-2026-6279: themefusion avada (fusion) builder Injection

Vulnerability summary

CVE-2026-6279 is a critical (CVSS 9.8) Injection vulnerability in themefusion avada (fusion) builder. EPSS estimates a 2.39% chance of exploitation in the next 30 days, higher than 83.7% of scored vulnerabilities. Fixed in 3.15.3.

Timeline

1. 21-05-2026
   PublishedVulnerability first disclosed.
2. 21-05-2026
   Last modifiedVulnerability information updated.

Description

The Avada Builder (fusion-builder) plugin for WordPress is vulnerable to Unauthenticated Remote Code Execution via PHP Function Injection in versions up to and including 3.15.2. This is due to the `wp_conditional_tags` case in `Fusion_Builder_Conditional_Render_Helper::get_value()` passing attacker-controlled values from a base64-decoded JSON blob directly to `call_user_func()` without any allowlist validation. This is exploitable by unauthenticated attackers through the `fusion_get_widget_markup` AJAX endpoint, which is registered for non-privileged (unauthenticated) users via `wp_ajax_nopriv_fusion_get_widget_markup`. The endpoint is protected only by a nonce (`fusion_load_nonce`), but this nonce is generated for user ID 0 and is deterministically exposed in the JavaScript output of any public-facing page containing a Post Cards (`[fusion_post_cards]`) or Table of Contents (`[fusion_table_of_contents]`) element. This makes it possible for unauthenticated attackers to execute arbitrary code on affected sites.

• CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.