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CVE-2026-87123— hbs vulnerable to Denial of Service via unhandled exception in async helper output escaping

Quick assessment

Affected
hbs hbs
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.

hbs 是一个用于 Handlebars 的 Express 视图引擎封装库。在 4.3.0 版本中，当通过 注册的异步辅助函数解析为一个对象，且该对象的 属性为真值但不可调用时，Node.js 进程会在输出转义阶段发生崩溃。Handlebars 的 函数会对任何具有真值 属性的值调用其 方法，因此这类值会抛出 。由于异步替换发生在渲染函数 块之外的后续事件循环 tick 中，该异常成为未捕获异常，导致进程终止且未发送响应。仅 4.3.0 版本受影响，因为引入抛出异常的转义逻辑是为了修复 CVE-2026-1623

CVSS 5.9 · Medium EPSS 0.41% · P35

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-87123

Vulnerability Information
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Vulnerability Title
hbs vulnerable to Denial of Service via unhandled exception in async helper output escaping
Source: CVE Program / CVE List V5
Vulnerability Description
hbs is an Express view engine wrapper for Handlebars. Version 4.3.0 can crash the Node.js process during output escaping when an async helper, registered with registerAsyncHelper, resolves to an object whose toHTML property is truthy but not callable. Handlebars escapeExpression calls the toHTML method on any value that has a truthy toHTML, so such a value throws a TypeError, and because the async substitution runs on a later tick outside the render function's try/catch, the throw is an uncaught exception that terminates the process without sending a response. Only version 4.3.0 is affected, since the throwing escape was introduced by the fix for CVE-2026-16231 and earlier versions do not escape async helper values. It can be triggered remotely when an async helper resolves to an externally influenced object such as parsed JSON. The issue is fixed in hbs 4.3.1, and users should upgrade to hbs 4.3.1 or later.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未捕获的异常
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
hbs hbs 4.3.0 ~ 4.3.1 -

II. Public POCs for CVE-2026-87123

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III. Intelligence Information for CVE-2026-87123

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Vendor Advisories for CVE-2026-87123 (1)

IV. Related Vulnerabilities

Same product: hbs
Same vendor: hbs
Same weakness: CWE-248

V. Comments for CVE-2026-87123

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