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Fencer Vulns
medium 5.3

CVE-2026-59868 json

js-yaml: YAML merge-key chains can force quadratic CPU consumption

published 2026-07-08 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-42302 , GHSA-g796-fgmg-93mv

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

Summary

js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.0, when merge keys are enabled, 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 version 5.2.0.

Patch / fix

  • npm js-yaml 5.2.0
  • nodeca js-yaml 5.2.0
  • nodejs22 hummingbird 1 22.23.1-2.hum1
  • nodejs22-bin hummingbird 1 22.23.1-2.hum1
  • nodejs22-npm hummingbird 1 10.9.8-1.22.23.1.2.hum1
  • nodejs22-libs hummingbird 1 22.23.1-2.hum1
  • nodejs22-npm-bin hummingbird 1 22.23.1-2.hum1
  • nodejs22-full-i18n hummingbird 1 22.23.1-2.hum1
  • rust hummingbird 1 1.96.1-1.hum1
  • cargo hummingbird 1 1.96.1-1.hum1

red hat advisories RHSA-2026:35272RHSA-2026:34975RHSA-2026:34478RHSA-2026:33866RHSA-2026:26994RHSA-2026:9455

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-59868 updated cvss 7.5

js-yaml: js-yaml: Denial of Service via quadratic CPU time parsing with merge keys

  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1788206196
    fixed: vendor fix RHSA-2026:61783
  • Red Hat Hardened Images rust 1.96.1-1.hum1, cargo 1.96.1-1.hum1, clippy 1.96.1-1.hum1, rustfmt 1.96.1-1.hum1, rust-gdb 1.96.1-1.hum1, rust-src 1.96.1-1.hum1, +47 more
    fixed: vendor fix RHSA-2026:34975
  • Red Hat Cryostat 4 js-yaml, grafana-infinity-datasource-npm, cryostat-openshift-console-plugin-npm, cryostat/cryostat-openshift-console-plugin-rhel9 Red Hat Gatekeeper 3 gatekeeper/gatekeeper-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-ui-rhel8, mta/mta-ui-rhel9 Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-ui-rhel8 Red Hat Multicluster Engine for Kubernetes multicluster-engine/console-mce-rhel9 Red Hat Network Observability Operator network-observability/network-observability-console-plugin-rhel9, network-observability/network-observability-console-plugin-pf5-rhel9
    +32 more products
    Red Hat Node HealthCheck Operator workload-availability/node-remediation-console-rhel8, workload-availability/node-remediation-console-rhel9, workload-availability/node-healthcheck-rhel9-operator, workload-availability/node-healthcheck-operator-bundle, workload-availability/node-healthcheck-must-gather-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-console-plugin-419-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9 Red Hat OpenShift Pipelines openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-ui-rhel9, openshift-pipelines/pipelines-console-plugin-rhel8, openshift-pipelines/pipelines-console-plugin-rhel9, openshift-pipelines/pipelines-console-plugin-pf5-rhel9 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9, openshift-service-mesh/kiali-ossmc-rhel9, openshift-service-mesh/kiali-rhel9-operator, openshift-service-mesh/kiali-operator-bundle Red Hat 3scale API Management Platform 2 3scale-amp21/system, 3scale-amp22/system, 3scale-amp2/system-rhel7, 3scale-amp2/system-rhel8, 3scale-amp2/system-rhel9 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/console-rhel9 Red Hat Advanced Cluster Security 4 advanced-cluster-security/rhacs-main-rhel8, advanced-cluster-security/rhacs-main-rhel9 Red Hat AMQ Broker 7 js-yaml Red Hat Ansible Automation Platform 2 automation-gateway, automation-controller, automation-platform-ui, automation-eda-controller, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9, +6 more Red Hat build of Apache Camel - HawtIO 4 js-yaml Red Hat build of Apache Camel for Spring Boot 4 js-yaml Red Hat build of Apicurio Registry 3 apicurio/apicurio-registry-ui-rhel8, apicurio/apicurio-registry-ui-rhel9 Red Hat Build of Keycloak js-yaml Red Hat Build of Podman Desktop rh-podman-desktop.git Red Hat Ceph Storage 9 rhceph/alloy-rhel10 Red Hat Connectivity Link 1 rhcl-1/rhcl-console-plugin-rhel9 Red Hat Data Grid 8 js-yaml Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Directory Server 11 389-ds-base Red Hat Directory Server 12 389-ds-base Red Hat Directory Server 13 389-ds-base Red Hat Discovery 2 discovery/discovery-server-rhel9 1788205779 Red Hat Edge Manager 1 rhem/flightctl-ui-rhel9, rhem/flightctl-ui-rhel10, rhem/flightctl-ui-ocp-rhel9, rhem/flightctl-ui-ocp-rhel10 Red Hat Enterprise Linux 7 rhsm-gtk, python-syspurpose, subscription-manager, subscription-manager-gui, subscription-manager-rhsm, subscription-manager-cockpit, +5 more Red Hat Enterprise Linux 8 pcs, grafana, mozjs60, pcs-snmp, grafana-loki, grafana-mssql, +11 more Red Hat Enterprise Linux 9 gjs, pcs, rust, cargo, clippy, grafana, +13 more Red Hat Enterprise Linux 10 rust, grafana Red Hat Enterprise Linux AI (RHEL AI) 3 rust, rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9 Red Hat Hardened Images dotnet-hostfxr-8.0 8.0.28-1.hum1, dotnet-runtime-8.0 8.0.28-1.hum1, aspnetcore-runtime-8.0 8.0.28-1.hum1, dotnet-runtime-dbg-8.0 8.0.28-1.hum1, dotnet-apphost-pack-8.0 8.0.28-1.hum1, dotnet-targeting-pack-8.0 8.0.28-1.hum1, +2 more Red Hat JBoss Enterprise Application Platform 7 js-yaml Red Hat JBoss Enterprise Application Platform 8 js-yaml Red Hat JBoss Enterprise Application Platform Expansion Pack js-yaml
    not affected: vulnerable code not present

15 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/nodeca/js-yaml/security/advisories/GHSA-g796-fgmg-93mv referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm js-yaml
>=5.0.0, <5.2.0
5.2.0

Affected products

  • nodeca js-yaml

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.