CVE-2026-53550: js-yaml is a JavaScript YAML parser and dumper

Q: How do I fix CVE-2026-53550?

js-yaml: upgrade to 3.15.0, 4.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-53550 being exploited?

CVE-2026-53550 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-53550 affect?

CVE-2026-53550 affects js-yaml. Severity is medium (CVSS 5.3). js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This

Q: How urgent is CVE-2026-53550?

Priority 37/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-53550 is a medium-severity flaw (CVSS 5.3) affecting js-yaml. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in me

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-407
Published	2026-06-22
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: nodeca

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-22 16:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

nodeca js-yaml UPGRADE

Affected: < 3.15.0 · >= 4.0.0 and < 4.2.0

Fixed in: 3.15.0, 4.2.0

Safe to downgrade to: a release before 4.0.0

1. Check installed version

npm ls js-yaml

2. UPGRADE to 3.15.0

npm install js-yaml@">=3.15.0"

3. If no update is available yet, DOWNGRADE to a release before 4.0.0

npm view js-yaml versions npm install js-yaml@"<4.0.0"

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-2026-53550?

js-yaml: upgrade to 3.15.0, 4.2.0. Exact commands for each OS are on this page.

Is CVE-2026-53550 being exploited?

CVE-2026-53550 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-2026-53550 affect?

CVE-2026-53550 affects js-yaml. Severity is medium (CVSS 5.3). js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This

How urgent is CVE-2026-53550?

Priority 37/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Node.js vulnerabilities

Related CVEs

CVE-2026-59870 HIGH 7.5 UPGRADE js-yaml is a JavaScript YAML parser and dumper
CVE-2026-59869 HIGH 7.5 UPGRADE js-yaml is a JavaScript YAML parser and dumper
CVE-2026-59868 MEDIUM 5.3 UPGRADE js-yaml is a JavaScript YAML parser and dumper

References

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