--- id: CVE-2026-84375 title: js-yaml is a JavaScript YAML parser and dumper summary: >- js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias… severity: high cvss: 7.5 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H' cwe: - CWE-400 - CWE-407 - CWE-835 vendor: js-yaml product: js-yaml affected: - 'js-yaml >= 4.0.0, < 4.3.2' - 'js-yaml >= 3.0.0, < 3.15.2' patched: - js-yaml 4.3.2 - js-yaml 3.15.2 published: '2026-09-01' updated: '2026-09-09' sourceUpdated: '2026-09-09T21:09:13.080' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84375' references: - url: >- https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639 label: security-advisories@github.com - url: >- https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480 label: security-advisories@github.com - url: >- https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b label: security-advisories@github.com - url: 'https://github.com/nodeca/js-yaml/pull/797' label: security-advisories@github.com - url: 'https://github.com/nodeca/js-yaml/releases/tag/3.15.2' label: security-advisories@github.com - url: 'https://github.com/nodeca/js-yaml/releases/tag/4.3.2' label: security-advisories@github.com - url: 'https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh' label: security-advisories@github.com - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-84375' - url: 'https://github.com/advisories/GHSA-2883-xcg3-v3hh' - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84375.json - url: 'https://access.redhat.com/security/cve/CVE-2026-84375' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2527118' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-84375' - url: 'https://access.redhat.com/errata/RHSA-2026:62810' - url: 'https://access.redhat.com/errata/RHSA-2026:63165' - url: 'https://access.redhat.com/errata/RHSA-2026:62813' - url: 'https://access.redhat.com/errata/RHSA-2026:66084' - url: 'https://access.redhat.com/errata/RHSA-2026:67711' - url: 'https://access.redhat.com/errata/RHSA-2026:67714' - url: 'https://access.redhat.com/errata/RHSA-2026:67279' - url: 'https://access.redhat.com/errata/RHSA-2026:68044' - url: 'https://access.redhat.com/errata/RHSA-2026:68253' - url: 'https://access.redhat.com/errata/RHSA-2026:68006' - url: 'https://access.redhat.com/errata/RHSA-2026:68254' - url: 'https://access.redhat.com/errata/RHSA-2026:63164' - url: 'https://access.redhat.com/errata/RHSA-2026:68681' - url: 'https://access.redhat.com/errata/RHSA-2026:67724' - url: 'https://access.redhat.com/errata/RHSA-2026:68754' - url: 'https://access.redhat.com/errata/RHSA-2026:68687' - url: 'https://access.redhat.com/errata/RHSA-2026:68689' - url: 'https://access.redhat.com/errata/RHSA-2026:68691' - url: 'https://access.redhat.com/errata/RHSA-2026:68690' - url: 'https://access.redhat.com/errata/RHSA-2026:69289' - url: 'https://access.redhat.com/errata/RHSA-2026:71113' - url: 'https://access.redhat.com/errata/RHSA-2026:70593' - url: 'https://access.redhat.com/errata/RHSA-2026:71210' - url: 'https://access.redhat.com/errata/RHSA-2026:71179' - url: 'https://access.redhat.com/errata/RHSA-2026:70047' - url: 'https://access.redhat.com/errata/RHSA-2026:69998' - url: 'https://access.redhat.com/errata/RHSA-2026:70027' tags: - nvd - ghsa - npm - csaf - vex - red-hat epss: 0.00529 epssPercentile: 0.42227 aliases: - GHSA-2883-xcg3-v3hh ecosystem: npm ingestedAt: '2026-09-08T22:12:30.968Z' --- ## Overview js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2 and 4.3.2, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. This issue is fixed in versions 3.15.2 and 4.3.2. ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Package advisory (CVE-2026-84375) Affected packages: - `js-yaml >= 4.0.0, < 4.3.2` - `js-yaml >= 3.0.0, < 3.15.2` Patched in: - `js-yaml 4.3.2` - `js-yaml 3.15.2` Source: https://github.com/advisories/GHSA-2883-xcg3-v3hh ## Vendor advisories - **RHSA-2026:62810** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:62810) - **RHSA-2026:63165** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:63165) - **RHSA-2026:62813** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:62813) - **RHSA-2026:66084** · Red Hat · fixed in: Red Hat Quay 3.10 · released 2026-09-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:66084) - **Red Hat VEX** · Moderate · affected: Ansible Automation Orchestrator 2026, Multicluster Engine for Kubernetes, Node HealthCheck Operator, OpenShift Lightspeed, OpenShift Pipelines, Red Hat Advanced Cluster Management for Kubernetes 2, … · no fix planned: Red Hat Ansible Automation Platform 2, Red Hat Directory Server 11, Red Hat Directory Server 12, Red Hat Directory Server 13, … · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-84375.json) - **RHSA-2026:67711** · Red Hat · fixed in: Red Hat Advanced Cluster Security for Kubernetes 4.10 · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67711) - **RHSA-2026:67714** · Red Hat · fixed in: Red Hat Advanced Cluster Security for Kubernetes 4.11 · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67714) - **RHSA-2026:67279** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.7 · released 2026-09-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:67279) - **RHSA-2026:68044** · Red Hat · fixed in: Red Hat Edge Manager 1.1 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68044) - **RHSA-2026:68253** · Red Hat · fixed in: Red Hat Edge Manager 1.1 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68253) - **RHSA-2026:68006** · Red Hat · fixed in: Red Hat Edge Manager 1.2 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68006) - **RHSA-2026:68254** · Red Hat · fixed in: Red Hat Edge Manager 1.2 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68254) - **RHSA-2026:63164** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:63164) - **RHSA-2026:69289** · Red Hat · fixed in: Red Hat Discovery 2 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69289) - **RHSA-2026:71113** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.6 for RHEL 9 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71113) - **RHSA-2026:70593** · Red Hat · fixed in: Network Observability (NETOBSERV) 1.12.3 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:70593) - **RHSA-2026:71210** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.5 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71210) - **RHSA-2026:71179** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.6 · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71179) - **RHSA-2026:70047** · Red Hat · fixed in: Red Hat Container Native Virtualization 4.12 · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:70047) - **RHSA-2026:69998** · Red Hat · fixed in: Red Hat Container Native Virtualization 4.14 · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:69998) - **RHSA-2026:70027** · Red Hat · fixed in: Red Hat Container Native Virtualization 4.16 · released 2026-09-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:70027)