CVE-2026-87123 (GCVE-0-2026-87123)
Vulnerability from cvelistv5 – Published: 2026-09-11 09:50 – Updated: 2026-09-11 10:29
VLAI
EPSS
VEX
Title
hbs vulnerable to Denial of Service via unhandled exception in async helper output escaping
Summary
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.
Severity
5.9 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-11 10:28 UTC
CWE
- CWE-248 - Uncaught Exception
Assigner
openjs
CNA
References
Impacted products
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