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CVE-2026-33916— Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection

Quick assessment

Affected
handlebars-lang handlebars.js
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
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resolvePartial函数未防范原型链遍历，可能导致原型污染，进而引发反射型或存储型跨站脚本攻击。

CVSS 4.7 · Medium EPSS 0.38% · P30

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-33916

Vulnerability Information
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Vulnerability Title
Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection
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, `resolvePartial()` in the Handlebars runtime resolves partial names via a plain property lookup on `options.partials` without guarding against prototype-chain traversal. When `Object.prototype` has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS. Version 4.7.9 fixes the issue. Some workarounds are available. Apply `Object.freeze(Object.prototype)` early in application startup to prevent prototype pollution. Note: this may break other libraries, and/or use the Handlebars runtime-only build (`handlebars/runtime`), which does not compile templates and reduces the attack surface.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
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resolvePartial函数未防范原型链遍历，可能导致原型污染，进而引发反射型或存储型跨站脚本攻击。
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-2026-33916

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III. Intelligence Information for CVE-2026-33916

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Patches & Fixes for CVE-2026-33916 (1)

Vendor Advisories for CVE-2026-33916 (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-2026-33939 7.5 HIGH Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation

IV. Related Vulnerabilities

Same product: handlebars.js
Same vendor: handlebars-lang
Same weakness: CWE-79

V. Comments for CVE-2026-33916

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