CVE-2026-21713: A flaw in Node.js HMAC verification uses a non-constant-time comparison when validating user-provided signatur

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2026-21713 is a medium-severity flaw (CVSS 5.9) affecting node.js. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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,

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-208
Published	2026-03-30
Last modified	2026-08-19

Publisher (CNA): HackerOne · Vendor: nodejs

Last updated 2026-08-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-30 20:16 UTCPublished CVE record published
2026-08-19 13:36 UTCUpdated Record last modified

nodejs node.js UPGRADE

Affected: <= 20.20.1 · >= 22.0.0 and <= 22.22.1 · >= 24.0.0 and <= 24.14.0 · >= 25.0.0 and <= 25.8.1

Fixed in: newer than 25.8.1

Safe to downgrade to: a release before 22.0.0

1. Check installed version

apt-cache policy node.js || rpm -q node.js || node.js --version

2. UPGRADE to newer than 25.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade node.js

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade node.js

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 22.0.0 (Debian / Ubuntu)

apt-cache madison node.js sudo apt install node.js=<VERSION_BEFORE_22.0.0> sudo apt-mark hold node.js

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list node.js sudo dnf downgrade node.js-<VERSION_BEFORE_22.0.0> sudo dnf versionlock add node.js

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-21713?

node.js: upgrade to newer than 25.8.1. Exact commands for each OS are on this page.

Is CVE-2026-21713 being exploited?

CVE-2026-21713 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-21713 affect?

CVE-2026-21713 affects node.js. Severity is medium (CVSS 5.9). 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-re

How urgent is CVE-2026-21713?

Priority 33/100. Remotely exploitable, no login, no user action

Software pages

Node.js vulnerabilities

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References

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