{"id":"UBUNTU-CVE-2026-33938","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.","modified":"2026-06-30T18:17:56.746583429Z","published":"2026-03-27T21:17:00Z","upstream":["CVE-2026-33938"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33938"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33938"},{"type":"REPORT","url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r"},{"type":"REPORT","url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"},{"type":"REPORT","url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"},{"type":"REPORT","url":"https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"}],"affected":[{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.0.10-5"],"ecosystem_specific":{"binaries":[{"binary_name":"handlebars","binary_version":"3:4.0.10-5"},{"binary_version":"3:4.0.10-5","binary_name":"libjs-handlebars"},{"binary_name":"libjs-handlebars.runtime","binary_version":"3:4.0.10-5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33938.json"}},{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.1.0-1","3:4.5.3-1","3:4.7.2-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3:4.7.2-1","binary_name":"handlebars"},{"binary_name":"libjs-handlebars","binary_version":"3:4.7.2-1"},{"binary_name":"libjs-handlebars.runtime","binary_version":"3:4.7.2-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33938.json"}},{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.7.6+~4.1.0-2","3:4.7.7+~4.1.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"handlebars","binary_version":"3:4.7.7+~4.1.0-1"},{"binary_name":"libjs-handlebars","binary_version":"3:4.7.7+~4.1.0-1"},{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"libjs-handlebars.runtime"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33938.json"}},{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.7.7+~4.1.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"handlebars"},{"binary_name":"libjs-handlebars","binary_version":"3:4.7.7+~4.1.0-1"},{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"libjs-handlebars.runtime"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33938.json"}},{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.7.7+~4.1.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"handlebars"},{"binary_name":"libjs-handlebars","binary_version":"3:4.7.7+~4.1.0-1"},{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"libjs-handlebars.runtime"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33938.json"}},{"package":{"name":"node-handlebars","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/node-handlebars?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3:4.7.7+~4.1.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3:4.7.7+~4.1.0-1","binary_name":"handlebars"},{"binary_name":"libjs-handlebars","binary_version":"3:4.7.7+~4.1.0-1"},{"binary_name":"libjs-handlebars.runtime","binary_version":"3:4.7.7+~4.1.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-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"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}