{"cve":"CVE-2026-33938","nvd":{"published":"2026-03-27T21:17:27.587","modified":"2026-10-26T22:10:00.163","status":"Modified","description":"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 `{{> @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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","score":8.1},"cwes":["CWE-94","CWE-843","CWE-917"],"references":["https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2","https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9","https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r","https://access.redhat.com/errata/RHSA-2026:10175","https://access.redhat.com/errata/RHSA-2026:34342"],"products":["handlebarsjs:handlebars"],"source":"nvd","synced_at":"2026-10-26T22:26:44.656832877+00:00"},"epss":{"cve":"CVE-2026-33938","score":0.00721,"percentile":0.53683,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-3mfm-83xf-c92r","url":"https://osv.dev/vulnerability/GHSA-3mfm-83xf-c92r","summary":"Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block","modified":"2026-09-10T03:50:36.784657898Z","packages":[{"ecosystem":"npm","name":"handlebars","purl":"pkg:npm/handlebars","ranges":[">=4.0.0 <4.7.9"],"fixed":["4.7.9"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}