{"id":"CVE-2026-33940","aliases":["GHSA-xhpv-hc6g-r9c6"],"url":"https://o3.security/vulnerability/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 (`{{> (lookup ...)}}`) when context data is user-controlled.","published":"2026-03-27T21:11:10.719Z","modified":"2026-07-16T03:31:12.251302237Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"handlebars","fixedVersion":"4.7.9"}],"fix":{"url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","label":"handlebars-lang/handlebars.js@68d8df5"},"references":[{"type":"WEB","url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33940.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:10175"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:34342"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-33940"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33940.json"},{"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"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2452521"},{"type":"FIX","url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-16T03:31:12.251302237Z"}}