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CVE-2026-33937— Handlebars.js has JavaScript Injection via AST Type Confusion

Quick assessment

Affected
handlebars-lang handlebars.js
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

handlebars是一款语义化的Web模板系统。 Handlebars 4.7.8及之前版本存在安全漏洞，该漏洞源于Handlebars.compile函数对NumberLiteral AST节点的value字段处理不当，可能导致攻击者注入并执行任意JavaScript代码，引发服务器端远程代码执行。

CVSS 9.8 · Critical EPSS 1.74% · P77

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
handlebars-lang handlebars.js >= 4.0.0, < 4.7.9 affected
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I. Basic Information for CVE-2026-33937

Vulnerability Information
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Vulnerability Title
Handlebars.js has JavaScript Injection via AST Type Confusion
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
使用不兼容类型访问资源(类型混淆)
Source: CVE Program / CVE List V5
Vulnerability Title
handlebars 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
handlebars是一款语义化的Web模板系统。 Handlebars 4.7.8及之前版本存在安全漏洞，该漏洞源于Handlebars.compile函数对NumberLiteral AST节点的value字段处理不当，可能导致攻击者注入并执行任意JavaScript代码，引发服务器端远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
handlebars-lang handlebars.js >= 4.0.0, < 4.7.9 -

II. Public POCs for CVE-2026-33937

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7059 chars
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III. Intelligence Information for CVE-2026-33937

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Patches & Fixes for CVE-2026-33937 (1)

Vendor Advisories for CVE-2026-33937 (1)

Same Patch Batch · handlebars-lang · 2026-03-27 · 6 CVEs total

CVE-2026-33941 8.3 HIGH Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options
CVE-2026-33938 8.1 HIGH Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block
CVE-2026-33940 8.1 HIGH Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dy
CVE-2026-33939 7.5 HIGH Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation
CVE-2026-33916 4.7 MEDIUM Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection

IV. Related Vulnerabilities

Same product: handlebars.js
Same vendor: handlebars-lang
Same weakness: CWE-843

V. Comments for CVE-2026-33937

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