Inefficient Algorithmic Complexity in js-yaml (npm) - CVE-2026-53550
Published: July 3, 2026
Vulnerability identifier: #VU136864
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-53550
CWE-ID: CWE-407
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: npm Inc.
Affected software:
js-yaml (npm)
js-yaml (npm)
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to algorithmic complexity in merge-key processing in lib/loader.js when parsing crafted YAML documents with repeated aliases in a merge sequence. A remote attacker can submit a specially crafted YAML document to cause a denial of service.
The issue causes quadratic parse-time behavior relative to input size and can block a Node.js worker or event loop for seconds with a relatively small payload.
How to mitigate CVE-2026-53550
Install security update from vendor's website.