CVE-2026-87123
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk17th percentile - higher than 17% of all known CVEs
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.
Risk Assessment
An attacker could remotely crash the Node.js process, causing a denial of service (DoS). This may disrupt application and service availability.
Recommendation
Update hbs to version 4.3.1 or later. Verify that async helpers do not return objects with an invalid toHTML property.
Other vulnerabilities in hbs
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS