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CVE-2026-33939— Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation

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及之前版本存在代码问题漏洞，该漏洞源于模板包含未注册装饰器引用时导致未处理的TypeError，可能导致Node.js进程崩溃，引发单请求拒绝服务攻击。

CVSS 7.5 · High EPSS 0.76% · P54

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

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-2026-33939

Vulnerability Information
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Vulnerability Title
Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation
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, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, "n")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled templates; do not call `compile()` at request time.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对因果或异常条件的不恰当检查
Source: CVE Program / CVE List V5
Vulnerability Title
handlebars 代码问题漏洞
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及之前版本存在代码问题漏洞，该漏洞源于模板包含未注册装饰器引用时导致未处理的TypeError，可能导致Node.js进程崩溃，引发单请求拒绝服务攻击。
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)

Affected Products

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

II. Public POCs for CVE-2026-33939

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 8414 chars
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III. Intelligence Information for CVE-2026-33939

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Patches & Fixes for CVE-2026-33939 (1)

Vendor Advisories for CVE-2026-33939 (1)

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

CVE-2026-33937 9.8 CRITICAL Handlebars.js has JavaScript Injection via AST Type Confusion
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-2026-33916 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-754

V. Comments for CVE-2026-33939

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