Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block_CVE-2026-33938

{
    "lastseen": "",
    "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.",
    "published": "2026-03-27T21:05:42.485Z",
    "modified": "2026-04-01T03:55:42.796Z",
    "type": "cve",
    "title": "Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block",
    "source": "GitHub_M",
    "references": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r\nhttps://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2\nhttps://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9",
    "id": "CVE-2026-33938",
    "bulletinFamily": "",
    "cwe": [
        "CWE-94",
        "CWE-843"
    ],
    "cvelist": null,
    "sourceData": "handlebars-lang handlebars.js >= 4.0.0, < 4.7.9",
    "sourceHref": "",
    "cvss": {
        "score": 8.1,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "handlebars.js",
    "version": ">= 4.0.0, < 4.7.9",
    "vendor": "handlebars-lang",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}