CVE-2026-21713

Severity CVSS v4.0:

Pending analysis

Type:

Unavailable / Other

Publication date:

30/03/2026

Last modified:

10/05/2026

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.<br /> <br /> Node.js already provides timing-safe comparison primitives used elsewhere in the codebase, indicating this is an oversight rather than an intentional design decision.<br /> <br /> This vulnerability affects **20.x, 22.x, 24.x, and 25.x**.

Impact

Vector 3.x

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N CVSS v3.1 Severity and Metrics:

Base Score: 5.90 MEDIUM
Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): None
Availability (A): None

Base Score 3.x

5.90

Severity 3.x

MEDIUM

References to Advisories, Solutions, and Tools

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