{"id":"CVE-2026-33940","summary":"Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial","details":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). Without `compile()`,  the fallback compilation path in `invokePartial` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive  object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (`{{\u003e (lookup ...)}}`) when context data is user-controlled.","aliases":["GHSA-xhpv-hc6g-r9c6"],"modified":"2026-04-10T05:43:19.980111Z","published":"2026-03-27T21:11:10.719Z","related":["CGA-jvp9-2wq9-5g82"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33940.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-843","CWE-94"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33940.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-xhpv-hc6g-r9c6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33940"}],"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-2026-33940.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}