CVE-2026-33939

Fixed in a distro release EPSS <1%CVSS 7.5

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, "n")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled templates; do not call `compile()` at request time.

Published 2026-03-27 · CVE record · OSV

Products: handlebars-lang handlebars.js, Red Hat Cluster Observability Operator 1.5.0, Red Hat OpenShift Dev Spaces 3.27, Red Hat Cryostat 4, Logging Subsystem for Red Hat OpenShift, Red Hat Data Grid 8, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift AI (RHOAI), Red Hat Process Automation 7

Fixed upstream

Distro releases