Vulnerability in Themefusion Avada (Fusion) Builder
CVE-2026-6279
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.024 (83.7th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 83.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.032 · newest: 0.024 · change: -0.008
Affected products
- Themefusion Avada (Fusion) Builder — versions 0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.wordfence.com/threat-intel/vulnerabilities/id/5dc72d78-d47c-4b36-8d69-8672e…
- plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/helpers/class-fusio…
- plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/inc/helpers/class…
- plugins.trac.wordpress.org/browser/fusion-builder/trunk/shortcodes/fusion-widge…
- plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/shortcodes/fusion…
- plugins.trac.wordpress.org/browser/fusion-builder/trunk/shortcodes/fusion-widge…
- plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/shortcodes/fusion…
- plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/class-fusion-builde…
- plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/inc/class-fusion-…
- plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/helpers/class-fusio…
Frequently asked questions
- What is CVE-2026-6279?
- CVE-2026-6279 is a critical-severity vulnerability in Themefusion Avada (Fusion) Builder, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 9.8/10. Published 2026-05-21.
- How severe is CVE-2026-6279?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2026-6279 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.