{"id":"CVE-2026-33940","state":"PUBLISHED","title":"Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial","description":"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.","publishedAt":"2026-03-27T21:11:10.719Z","updatedAt":"2026-09-04T12:04:53.335Z","severity":{"score":8.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["handlebars-lang handlebars.js"],"affected":[{"vendor":"handlebars-lang","product":"handlebars.js","versions":[{"version":">= 4.0.0, < 4.7.9","status":"affected"}]}],"references":["https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6","https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","https://access.redhat.com/security/cve/CVE-2026-33940","https://bugzilla.redhat.com/show_bug.cgi?id=2452521","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33940.json","https://access.redhat.com/errata/RHSA-2026:34342","https://access.redhat.com/errata/RHSA-2026:10175"],"weaknesses":["CWE-94","CWE-843"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33940.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33940","state":"PUBLISHED","datePublished":"2026-03-27T21:11:10.719Z","dateUpdated":"2026-09-04T12:04:53.335Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-24T19:50:52.103Z"},"containers":{"cna":{"title":"Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"handlebars-lang","product":"handlebars.js","versions":[{"version":">= 4.0.0, < 4.7.9","status":"affected"}]}],"references":[{"url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6","name":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","name":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","tags":["x_refsource_MISC"]},{"url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","name":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-94","lang":"en","description":"CWE-94: Improper Control of Generation of Code ('Code Injection')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-843","lang":"en","description":"CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-27T21:11:10.719Z"},"source":{"advisory":"GHSA-xhpv-hc6g-r9c6","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-31T00:00:00+00:00","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3","id":"CVE-2026-33940"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-01T03:55:41.422Z"}},{"title":"handlebars.js: Handlebars.js: Arbitrary code execution via crafted template context","descriptions":[{"lang":"en","value":"A flaw was found in Handlebars.js. 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