CVE WatchJul 9, 2026

CVE-2026-53550

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

CVSS

5.3

Medium

EPSS

0.3%

p18

KEV

—

Exploit Today

0-100

Published: Jun 22, 2026 · Last modified: Jul 9, 2026 · CWE-407

EPSS · 30d

0.3%EPSS · 30 days0.3%

2026-06-302026-07-20

Technical description

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.

Official references

github.comhttps://github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68

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