CVE-2026-53550

NameCVE-2026-53550
Descriptionjs-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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
node-js-yaml (PTS)bullseye3.14.1+dfsg+~3.12.6-2vulnerable
bookworm, trixie4.1.0+dfsg+~4.0.5-7vulnerable
forky, sid4.1.1+dfsg+~4.0.9-1vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
node-js-yamlsource(unstable)(unfixed)

Notes

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

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