CVE-2026-59870

Description

js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 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. This issue is fixed in version 5.2.1.

CVSS Metrics

• v3.1•MEDIUM•Score: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Techniques & Countermeasures

• CWE-407•Inefficient Algorithmic Complexity

  An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

Affected Systems

• nodeca•js-yaml

  ≥ 5.0.0, < 5.2.1

• Npm•js-yaml

  ≥ 5.0.0, < 5.2.1

References (5)

• https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm
• https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe
• https://github.com/nodeca/js-yaml/releases/tag/5.2.1
• https://nvd.nist.gov/vuln/detail/CVE-2026-59870
• https://github.com/nodeca/js-yaml