{"id":"CVE-2026-33937","aliases":["GHSA-2w6w-674q-4c4q"],"url":"https://o3.security/vulnerability/CVE-2026-33937","summary":"Handlebars.js has JavaScript Injection via AST Type Confusion","details":"Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a  `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable.","published":"2026-03-27T21:03:46.748Z","modified":"2026-09-06T03:30:21.683476121Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.01704,"percentile":0.7591,"asOf":"2026-09-11"},"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-2026-33937.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-2026-33937"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33937.json"},{"type":"ADVISORY","url":"https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2w6w-674q-4c4q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33937"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2452523"},{"type":"FIX","url":"https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-06T03:30:21.683476121Z"}}