High [CVE-2026-59869] Denial of Service via crafted YAML documents

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. A remote attacker could exploit this vulnerability by providing a specially crafted YAML document containing a chain of mappings with merge keys.

This could cause the parser to consume excessive CPU resources, leading to a Denial of Service (DoS) for the affected system. This vulnerability is rated as Important.

Red Hat products utilizing `js-yaml` to process untrusted YAML input are susceptible to a denial of service, as a remote attacker can provide a crafted document that consumes excessive CPU resources. This is considered Important due to the potential for service disruption without requiring authentication or complex attack vectors.

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-606.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Streams for Apache Kafka 3.2.1; multicluster engine for Kubernetes 2.10; multicluster engine for Kubernetes 2.11; and 46 more.