Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection
Summary
Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection
Original description
The description as published by the source.
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, resolvePartial() in the Handlebars runtime resolves partial names via a plain property lookup on options.partials without guarding against prototype-chain traversal. When Object.prototype has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS. Version 4.7.9 fixes the issue. Some workarounds are available. Apply Object.freeze(Object.prototype) early in application startup to prevent prototype pollution. Note: this may break other libraries, and/or use the Handlebars runtime-only build (handlebars/runtime), which does not compile templates and reduces the attack surface.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-33916 node-handlebars
- Ubuntu UBUNTU-CVE-2026-33916 node-handlebars
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- web github.com