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MEDIUM

CVE-2026-59870

CVSS v3

5.3

MEDIUM

EPSS Score

0.7 %

exploit probability, as of 2026-10-17

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • js-yamlnpmfrom 5.0.0 · fixed in 5.2.1

Vendor advisories

  • CVE-2026-59870 Red Hat Product Security136 products fixed · 1 known affected

    js-yaml: js-yaml: Denial of Service via crafted YAML ordered-map document

    discovery/discovery-ui-rhel9 as a component of Red Hat Discovery 2

  • RHSA-2026:35272 Red Hat Product Security17 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

  • RHSA-2026:34975 Red Hat Product Security39 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

  • RHSA-2026:34478 Red Hat Product Security17 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

  • RHSA-2026:33866 Red Hat Product Security17 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

  • RHSA-2026:26994 Red Hat Product Security9 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

3 more advisories

Full record on NVD

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-07-08
Last Modified
2026-07-08
GitHub Advisory
GHSA-724g-mxrg-4qvm

Frequently asked questions

What is CVE-2026-59870?

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.

Is CVE-2026-59870 actively exploited?

Active exploitation of CVE-2026-59870 has not been confirmed. Its EPSS score was 0.7% on 2026-10-17, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-59870?

CVE-2026-59870 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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