{"cve":"CVE-2026-33939","nvd":{"published":"2026-03-27T22:16:20.857","modified":"2026-10-26T22:10:00.163","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-754","CWE-248"],"references":["https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-9cx6-37pm-9jff","https://access.redhat.com/errata/RHSA-2026:10175","https://access.redhat.com/errata/RHSA-2026:34342"],"products":["handlebarsjs:handlebars"],"source":"nvd","synced_at":"2026-10-26T22:26:44.656832877+00:00"},"epss":{"cve":"CVE-2026-33939","score":0.00627,"percentile":0.49768,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-9cx6-37pm-9jff","url":"https://osv.dev/vulnerability/GHSA-9cx6-37pm-9jff","summary":"Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation","modified":"2026-09-10T03:51:00.150731044Z","packages":[{"ecosystem":"npm","name":"handlebars","purl":"pkg:npm/handlebars","ranges":[">=4.0.0 <4.7.9"],"fixed":["4.7.9"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}