---
id: CVE-2026-59869
title: js-yaml is a JavaScript YAML parser and dumper
summary: >-
  js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 before 3.15.0 and
  from 4.0.0 before 4.3.0, js-yaml can spend quadratic CPU time parsing a
  document whose size grows only linearly when a chain of mappings uses merge
  keys where e…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-407
vendor: nodeca
product: js-yaml
affected:
  - 'js-yaml >= 3.0.0, < 3.15.0'
  - 'js-yaml >= 4.0.0, < 4.3.0'
patched:
  - js-yaml 4.3.0
published: '2026-07-08'
updated: '2026-07-13'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-59869'
references:
  - url: >-
      https://github.com/nodeca/js-yaml/commit/24f13e79ee1343a7e30bd6f6c9d9cdbf0ac9b2b7
    label: security-advisories@github.com
  - url: >-
      https://github.com/nodeca/js-yaml/commit/59423c6f8cdc78742ac00e25a4dd39ef16b702e4
    label: security-advisories@github.com
  - url: 'https://github.com/nodeca/js-yaml/releases/tag/3.15.0'
    label: security-advisories@github.com
  - url: 'https://github.com/nodeca/js-yaml/releases/tag/4.3.0'
    label: security-advisories@github.com
  - url: 'https://github.com/nodeca/js-yaml/security/advisories/GHSA-52cp-r559-cp3m'
    label: security-advisories@github.com
  - url: 'https://github.com/nodeca/js-yaml/security/advisories/GHSA-52cp-r559-cp3m'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00585
epssPercentile: 0.45611
ingestedAt: '2026-07-13T15:27:34.170Z'
---

## Overview

js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 before 3.15.0 and from 4.0.0 before 4.3.0, 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 versions 3.15.0 and 4.3.0.

## Affected

- `js-yaml >= 3.0.0, < 3.15.0`
- `js-yaml >= 4.0.0, < 4.3.0`

## Remediation

Upgrade past the affected range:

- `js-yaml 4.3.0`