{"id":"CVE-2026-33916","summary":"Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection","details":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `resolvePartial()` in the Handlebars runtime resolves partial names via a plain property lookup on `options.partials` without guarding against prototype-chain traversal. When `Object.prototype` has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS. Version 4.7.9 fixes the issue. Some workarounds are available. Apply `Object.freeze(Object.prototype)` early in application startup to prevent prototype  pollution. Note: this may break other libraries, and/or use the Handlebars runtime-only build (`handlebars/runtime`), which does not compile templates  and reduces the attack surface.","aliases":["GHSA-2qvq-rjwj-gvw9"],"modified":"2026-04-10T05:43:19.951515Z","published":"2026-03-27T21:00:48.624Z","related":["CGA-5q6v-px36-2cxq"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33916.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-1321","CWE-79"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33916.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-2qvq-rjwj-gvw9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33916"}],"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-2026-33916.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N"}]}