CVE-2026-21713

MEDIUM
5.9
CVSS Score
Published: March 30, 2026 at 07:07 PM UTC
Updated: August 19, 2026 at 02:45 PM UTC
1 product affected across 1 vendorNode.js

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Severity
MEDIUM5.9
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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**.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v ≤ 20.20.110.0 ≤ v < 10.*11.0 ≤ v < 11.*12.0 ≤ v < 12.*13.0 ≤ v < 13.*14.0 ≤ v < 14.*15.0 ≤ v < 15.*16.0 ≤ v < 16.*17.0 ≤ v < 17.*18.0 ≤ v < 18.*19.0 ≤ v < 19.*22.0.0 ≤ v ≤ 22.22.124.0.0 ≤ v ≤ 24.14.025.0.0 ≤ v ≤ 25.8.14.0 ≤ v < 4.*5.0 ≤ v < 5.*6.0 ≤ v < 6.*7.0 ≤ v < 7.*8.0 ≤ v < 8.*9.0 ≤ v < 9.*10.011.012.013.014.015.016.017.018.019.020.20.122.22.124.14.025.8.14.05.06.07.08.09.0
Affected range stops below 10.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 11.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 12.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 13.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 14.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 15.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 16.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 17.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 18.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 19.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 6.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 7.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 8.*, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.*, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (1)

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.9MEDIUMhackerone
Vector?

Quick Info

StatusANALYZED
CWE
CWE-208

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