CVE-2026-59870
High
Description
js-yaml is a JavaScript YAML parser and dumper. Prior to 3.15.1, 4.3.1, and 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. In v3 and v4, !!omap is active and exploitable by default. v5 doesn't use !!omap by default, and the chances of activating it are very low.This issue is fixed in 3.15.1, 4.3.1, and 5.2.1.
SeverityHigh
CVSS7.5
Exploit probability—
ProductNodeca Js-yaml
PublishedJul 8, 2026
First seenJul 8, 2026
Weakness typeCWE-407CWE-407
How to fix
Update
- nodeca js-yaml5.2.1 or later
- js-yaml5.2.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| nodeca js-yaml | 5.0.0 ≤ v < 5.2.1 | 5.2.1 |
| js-yamlnpm | 5.0.0 ≤ v < 5.2.1 | 5.2.1 |
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