CVE-2026-33938

Fixed in a distro release EPSS <1%CVSS 8.1

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{> @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). The `compile()` method is absent, eliminating the vulnerable fallback path. Second, audit registered helpers for any that write arbitrary values to context objects. Helpers should treat context data as read-only. Third, avoid registering helpers from third-party packages (such as `handlebars-helpers`) in contexts where templates or context data can be influenced by untrusted input.

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 Developer Hub, 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 OpenShift Dev Spaces, Red Hat Process Automation 7

Fixed upstream

Distro releases