CVE-2026-59869
js-yaml: YAML merge-key chains can force quadratic CPU consumption
7.5
HIGH
CVSS 3.1
EPSS 0.37%
Description
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.
How to fix CVE-2026-59869
To remediate CVE-2026-59869, upgrade the affected package to a fixed version below.
- —upgrade to 3.15.0 or later
Is CVE-2026-59869 being exploited?
Low — EPSS is 0.4%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 3.0.0, < 3.15.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |