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Fencer Intel
medium 5.3

CVE-2026-53550 json

js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases

published 5mo ago modified 17d ago also EUVD-2026-38256 , GHSA-h67p-54hq-rp68

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.

Patch / fix

  • npm js-yaml 3.15.0, 4.2.0
  • nodeca js-yaml 3.15.0, 4.2.0
  • node-js-yaml Debian 14 4.2.0+~4.0.9-1

debian advisories DEBIAN-CVE-2026-53550

  • nodejs24 hummingbird 1 24.18.0-0.3.hum1
  • nodejs24-bin hummingbird 1 24.18.0-0.3.hum1
  • nodejs24-npm hummingbird 1 11.16.0-1.24.18.0.0.3.hum1
  • nodejs24-libs hummingbird 1 24.18.0-0.3.hum1
  • nodejs24-npm-bin hummingbird 1 24.18.0-0.3.hum1
  • nodejs24-full-i18n hummingbird 1 24.18.0-0.3.hum1
  • nodejs25 hummingbird 1 25.9.0-1.3.hum1
  • nodejs25-bin hummingbird 1 25.9.0-1.3.hum1

red hat advisories RHSA-2026:38236RHSA-2026:37534RHSA-2026:33866

  • velociraptor openSUSE Tumbleweed 0.76.7.0.git145.b60ef1146-1.1
  • agama-web-ui openSUSE Tumbleweed 24+0.a836cced5-52.1
  • agama-integration-tests openSUSE Tumbleweed 1785848065.5562c7c-4.1
  • agama-web-ui openSUSE Leap 16.0 17+673.b97ba64d6-160000.12.1
  • python-pytest-html openSUSE Leap 16.0 4.1.1-bp160.3.1
  • python-pydata-sphinx-theme openSUSE Tumbleweed 0.19.0-1.1
  • python-pytest-html openSUSE Tumbleweed 4.2.0-3.1

opensuse advisories openSUSE-SU-2026:12070-1openSUSE-SU-2026:11680-1openSUSE-SU-2026:11452-1openSUSE-SU-2026:21448-1openSUSE-SU-2026:21176-1openSUSE-SU-2026:11148-1

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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-2026-53550 updated cvss 5.3

js-yaml: js-yaml: Denial of Service via crafted YAML merge keys

  • Red Hat Cryostat 4 js-yaml, grafana-infinity-datasource-npm, cryostat-openshift-console-plugin-npm, cryostat/cryostat-openshift-console-plugin-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 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
    +25 more products
    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 2 openshift-service-mesh/kiali-rhel8, openshift-service-mesh/kiali-ossmc-rhel8 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 Discovery 2 discovery/discovery-ui-rhel9 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 8 grafana, grafana-loki, grafana-mssql, grafana-mysql, grafana-selinux, grafana-graphite, +8 more Red Hat Enterprise Linux 9 grafana, grafana-selinux Red Hat Enterprise Linux 10 grafana
    affected: workaround, no fix available “Fix deferred”
  • 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
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Fuse 7 js-yaml
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images nodejs20
    affected: workaround, no fix planned “Will not fix”
  • 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 Red Hat OpenShift Container Platform 4 openshift4/ose-console, openshift4/ose-console-rhel9, openshift4/ose-monitoring-plugin-rhel8, openshift4/ose-monitoring-plugin-rhel9, openshift4/ose-agent-installer-ui-rhel9 Red Hat OpenShift Container Platform 5 openshift5/ose-console-rhel9, openshift5/ose-monitoring-plugin-rhel9, openshift5/nmstate-console-plugin-rhel9, openshift5/ose-agent-installer-ui-rhel9 Red Hat OpenShift Dev Spaces devspaces/code-rhel9, devspaces/dashboard-rhel9
    affected: workaround, no fix available “Fix deferred”

10 more affected, 5 more fixed, 13 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
none
Automatable
yes
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68 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

Affected packages

ecosystem package affected fixed in
npm js-yaml
>=4.0.0, <4.2.0
<3.15.0
4.2.0
3.15.0

Affected products

  • nodeca js-yaml

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity

References

Sources

Fencer Intel 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.

The maintainers of nodeca/js-yaml published their own advisory on GitHub. Reviewed sources take precedence over it.

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