{"id":"CVE-2026-33938","summary":"Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block","details":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{\u003e @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). The `compile()` method is  absent, eliminating the vulnerable fallback path. Second, audit registered helpers for any that write arbitrary values to context objects. Helpers  should treat context data as read-only. Third, avoid registering helpers from third-party packages (such as `handlebars-helpers`) in  contexts where templates or context data can be influenced by untrusted input.","aliases":["GHSA-3mfm-83xf-c92r"],"modified":"2026-04-10T05:43:20.235888Z","published":"2026-03-27T21:05:42.485Z","related":["CGA-c25f-88w6-vhfv"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33938.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-2026-33938.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-3mfm-83xf-c92r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33938"}],"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-2026-33938.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"}]}