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 merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Nodeca
  • Js-yaml

No data.

No data.

References
Link Providers
https://github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-53550 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-53550 cve-icon
History

Mon, 29 Jun 2026 16:15:00 +0000

Type Values Removed Values Added
Description js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0, 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 merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0. 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 merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.

Sat, 27 Jun 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-1333
References
Metrics threat_severity

None

 threat_severity

Moderate

Tue, 23 Jun 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 22 Jun 2026 18:00:00 +0000

Type Values Removed Values Added
First Time appeared Nodeca
Nodeca js-yaml
Vendors & Products Nodeca
Nodeca js-yaml

Mon, 22 Jun 2026 15:45:00 +0000

Type Values Removed Values Added
Description js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0, 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 merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0.
Title js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases
Weaknesses CWE-407
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-06-22T14:59:14.906Z

Updated: 2026-06-29T15:06:58.346Z

Reserved: 2026-06-09T18:13:07.263Z

Link: CVE-2026-53550

cve-icon Vulnrichment

Updated: 2026-06-23T16:05:51.466Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-06-22T14:59:14Z

Links: CVE-2026-53550 - Bugzilla