CVE-2026-59870: Nodeca Js-Yaml

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

js-yaml is a JavaScript YAML parser and dumper. Prior to 3.15.1, 4.3.1, and 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. In v3 and v4, !!omap is active and exploitable by default. v5 doesn't use !!omap by default, and the chances of activating it are very low.This issue is fixed in 3.15.1, 4.3.1, and 5.2.1.

Affected products

• Nodeca Js-Yaml: from 5.0.0, before 5.2.1 (fixed in 5.2.1)

Published 2026-07-08. Last modified 2026-10-06.