CVE WatchAug 19, 2026

CVE-2026-21713

A flaw in Node.js HMAC verification uses a non-constant-time comparison when validating user-provided signatures, potentially leaking timing

CVSS

5.9

Medium

EPSS

0.4%

p32

KEV

—

Exploit Today

0-100

Published: Mar 30, 2026 · Last modified: Aug 19, 2026 · CWE-208

EPSS · 30d

0.4%EPSS · 30 days0.4%

2026-08-232026-09-21

Technical description

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**.

Official references

nodejs.orghttps://nodejs.org/en/blog/vulnerability/march-2026-security-releases

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