CVE-2026-59868

js-yaml: YAML merge-key chains can force quadratic CPU consumption

State: Published
Severity: 5.3 Medium
Published: Jul 8, 2026
Updated: Jul 9, 2026
Reserved: Jul 7, 2026

Description

js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.0, when merge keys are enabled, js-yaml can spend quadratic CPU time parsing a document whose size grows only linearly when a chain of mappings uses merge keys where each mapping merges the previous one. This issue is fixed in version 5.2.0.

Scores

CVSS	Score	Vector	Source
3.1	5.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L	GitHub_M

Weaknesses

CWE-407 Inefficient Algorithmic Complexity

Affected Products

Product	Versions
js-yamlnodeca	>= 5.0.0, < 5.2.0Affected

References

https://github.com/nodeca/js-yaml/security/advisories/GHSA-g796-fgmg-93mv
https://github.com/nodeca/js-yaml/commit/3105455b81dee69e0fd36e09ac0b2ccfdb54adc1
https://github.com/nodeca/js-yaml/releases/tag/5.2.0

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