CVE-2026-21713: Node.js

Medium severity, CVSS 5.9. EPSS: 0.4% chance of exploitation in the next 30 days.

A flaw in Node.js HMAC verification uses a non-constant-time comparison when validating user-provided signatures, potentially leaking timing information proportional to the number of matching bytes. Under certain threat models where high-resolution timing measurements are possible, this behavior could be exploited as a timing oracle to infer HMAC values. Node.js already provides timing-safe comparison primitives used elsewhere in the codebase, indicating this is an oversight rather than an intentional design decision. This vulnerability affects **20.x, 22.x, 24.x, and 25.x**.

Affected products

• Node.js Node.js: up to and including 20.20.1; from 22.0.0, up to and including 22.22.1; from 24.0.0, up to and including 24.14.0; from 25.0.0, up to and including 25.8.1

Published 2026-03-30. Last modified 2026-08-19.