Vulnerabilidad · Publicado 25/08/2026
hbs, motor de vistas para Express que envuelve Handlebars, presenta una vulnerabilidad de inyección HTML (CVE-2026-16231, CVSS 8.1) en su API registerAsyncHelper. El fallo permite a atacantes bypass del escaping automático de HTML, ya que los helpers asincronos retornan placeholders durante el primer renderizado que no son escapados correctamente, exponiendo aplicaciones web a XSS. Afecta aplicaciones Node.js en producción que usan templates dinámicos con helpers asincronos.
hbs is an Express view engine that wraps Handlebars. Its registerAsyncHelper API bypasses Handlebars' automatic HTML escaping: an async helper returns an opaque placeholder during the first render pass, so the double-brace expression escapes only the placeholder, and after rendering hbs substitutes the placeholder with the raw callback return value without escaping it, across the cached, uncached, and layout render paths. An application that passes attacker-influenced data, for example user-supplied content from a database, into an async helper callback can therefore have arbitrary HTML and JavaScript injected into the server-rendered page, resulting in stored or reflected cross-site scripting. Versions 2.1.0 through 4.2.1 are affected, and the issue is fixed in 4.3.0, which HTML-escapes async helper output. Applications that intentionally emit raw HTML from an async helper can opt in explicitly with hbs.SafeString. Users should upgrade to 4.3.0.
Score: 8.1/10 — Severidad: HIGH — Estado NIST: Received
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
CWE-79
Publicado en NIST NVD.