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

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.js是The Handlebars Templating Language开源的一个JavaScript语义模板引擎。 Handlebars.js 4.7.8及之前版本存在安全漏洞，该漏洞源于@partial-block特殊变量可通过助手函数被覆盖，可能导致攻击者执行任意JavaScript代码，引发服务器端远程代码执行。

CVSS 8.1 · High EPSS 0.84% · P57

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

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-2026-33938

Vulnerability Information
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Vulnerability Title
Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block
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, 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对生成代码的控制不恰当(代码注入)
Source: CVE Program / CVE List V5
Vulnerability Title
Handlebars.js 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Handlebars.js是The Handlebars Templating Language开源的一个JavaScript语义模板引擎。 Handlebars.js 4.7.8及之前版本存在安全漏洞，该漏洞源于@partial-block特殊变量可通过助手函数被覆盖，可能导致攻击者执行任意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)

Affected Products

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

II. Public POCs for CVE-2026-33938

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 10000 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-33938

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Patches & Fixes for CVE-2026-33938 (1)

Vendor Advisories for CVE-2026-33938 (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-2026-33940 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-94

V. Comments for CVE-2026-33938

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