CVE-2026-59868CWE-407

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

Medium · published July 8, 2026

CVSS v3.1
5.3
EPSS
1%
Percentile
50.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00644 · 50.2th percentile
Weakness
CWE-407 · Inefficient Algorithmic Complexity
Published
2026-07-08T15:18Z
EPSS history
Timeline
  • 08 JUL 15:18Z
    js-yaml: YAML merge-key chains can force quadratic CPU consumption
    cvelistv5