CVE-2026-59870

A flaw was found in js-yaml, a JavaScript YAML (YAML Ain't Markup Language) parser. An attacker could exploit this by providing a specially crafted YAML ordered-map document. This could lead to excessive CPU consumption, resulting in a denial of service (DoS) for applications processing the malicious YAML input.

js-yaml versions 5.0.0 through 5.2.0 are vulnerable to a denial of service via the omapTag.addItem() O(n^2) duplicate-key scan when parsing crafted YAML ordered-map documents with the YAML11_SCHEMA. This affects yaml.load() calls using that schema. Fixed in 5.2.1.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Avoid using the YAML11_SCHEMA when parsing untrusted YAML input, or upgrade to js-yaml 5.2.1 or later. Applications using the default schema (CORE_SCHEMA) are not affected.