High [CVE-2026-59870] Denial of Service via crafted YAML ordered-map document
This high-severity Red Hat Linux advisory covers CVE-2026-59870 affecting Red Hat Hardened Images, Red Hat Discovery 2.
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Summary
js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 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.
This issue is fixed in version 5.2.1. An attacker could exploit this by providing a specially crafted YAML ordered-map document.
This could lead to excessive CPU consumption, resulting in a denial of service (DoS) for applications processing the malicious YAML input. This affects yaml.load() calls using that schema.
Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770.
Affected Red Hat products: Red Hat Hardened Images; Red Hat Discovery 2.
- < 5.0.0
- < 5.2.1
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
- 5.2.1
- dotnet8-0-main-8.0.128-1.hum1
- nodejs26-main-26.4.0-1.3.hum1
- nodejs24-main-24.18.0-0.2.hum1
- rust-main-1.96.1-1.hum1
- nodejs22-main-22.23.1-2.hum1
- nodejs25-main-25.9.0-1.1.hum1
- yarnpkg-main-1.22.22-18.1.hum1
- nodejs20-main-20.20.2-1.hum1
- RHSA-2026:26994
- RHSA-2026:33866
- RHSA-2026:34478
- RHSA-2026:34975
- RHSA-2026:35272
- RHSA-2026:7378
- RHSA-2026:7655
- RHSA-2026:9455
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
Mitigation checklist
- Avoid using the YAML11_SCHEMA when parsing untrusted YAML input, or upgrade to js-yaml 5.2.1 or later. Applications using the default schema (CORE_SCHEMA) are not affected.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
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