{"id":"CVE-2026-33939","summary":"Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation","details":"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.","aliases":["GHSA-9cx6-37pm-9jff"],"modified":"2026-04-10T05:43:19.969097Z","published":"2026-03-27T21:08:24.664Z","related":["CGA-27f7-qfjw-jxj5"],"database_specific":{"cwe_ids":["CWE-754"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33939.json","cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33939.json"},{"type":"FIX","url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"},{"type":"WEB","url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"},{"type":"ADVISORY","url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33939"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/handlebars-lang/handlebars.js","events":[{"introduced":"bff5fab8f9d42e21950be00dcf1cedf4dc1a565b"},{"fixed":"dce542c9a660048d31f0981ac8a45c08b919bddb"}],"database_specific":{"versions":[{"introduced":"4.0.0"},{"fixed":"4.7.9"}]}}],"versions":["v4.0.0","v4.0.1","v4.0.10","v4.0.11","v4.0.12","v4.0.2","v4.0.3","v4.0.4","v4.0.5","v4.0.6","v4.0.7","v4.0.8","v4.0.9","v4.1.1","v4.1.2","v4.1.2-0","v4.2.0","v4.2.1","v4.3.0","v4.3.1","v4.3.2","v4.3.3","v4.3.4","v4.4.0","v4.4.1","v4.4.2","v4.4.3","v4.5.0","v4.5.1","v4.5.2","v4.5.3","v4.6.0","v4.7.0","v4.7.1","v4.7.2","v4.7.3","v4.7.4","v4.7.5","v4.7.6","v4.7.7","v4.7.8"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33939.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}