CVE-2026-106445

Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars lookupProperty returns Function.prototype.constructor before applying the prototype-access deny list because constructor is an own property of Function.prototype. When an attacker can render a controlled template with allowProtoMethodsByDefault enabled and an accessible function in the template context, the template can traverse from that function through its prototype to Function.prototype and then obtain the Function constructor through the own-property bypass. This permits attacker-controlled JavaScript to execute with the server application's privileges. This issue is fixed in version 4.7.10.

• CWE-184
• CWE-1289

• https://github.com/handlebars-lang/handlebars.js/commit/ceec388abe1d1aac8f6369860d5f390fa71ef4fa
• https://github.com/handlebars-lang/handlebars.js/pull/2185
• https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10
• https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-p8wg-vrv2-v86f

Published

Oct 6, 2026

Last Modified

Oct 7, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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