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Fencer Vulns
medium 5.9

CVE-2026-63402 json

i18next: Shared built-in corruption through inherited-key deepExtend recursion

published 2026-10-30 9 d ago modified 2026-11-05 4 d ago also EUVD-2026-114546

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits
0
none known

Summary

i18next is an internationalization framework for JavaScript. Prior to version 26.3.4, `deepExtend` in `src/utils.js` checks property existence with the in operator and recurses into inherited built-ins reached through `Object.prototype`. An application must explicitly pass attacker-controlled resource data to `addResourceBundle(lng, ns, data, deep, overwrite)` with both `deep: true` and `overwrite: true`. Source keys such as `hasOwnProperty`, `toString` and `valueOf` can then select shared inherited built-in function objects, and a nested value can overwrite a property of those objects process-wide. For example, making `Object.prototype.hasOwnProperty.call` non-callable causes subsequent uses, including i18next internals, to throw TypeError, resulting in unrecoverable denial of service and limited integrity impact. The `__proto__`/`constructor` guard does not prevent this mechanism because the corruption target is an inherited built-in function rather than the prototype object itself. Default calls without deep merging or with overwrite falsy are unaffected, and no standard i18next backend or integration uses the vulnerable configuration. This issue is distinct from the setPath/key-walking prototype-pollution flaws in i18next-fs-backend (CVE-2026-48713) and i18next-http-middleware (CVE-2026-48714). This issue is fixed in version 26.3.4.

Patch / fix

  • node-i18next Debian 14 26.7.1-1

debian advisories DEBIAN-CVE-2026-63402

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-2026-63402 updated cvss 5.9

i18next: i18next: Denial of Service via unsafe recursive object merging

  • Red Hat Cryostat 4 cryostat/cryostat-openshift-console-plugin-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-ui-rhel9 Red Hat Migration Toolkit for Virtualization migration-toolkit-virtualization/mtv-console-plugin-rhel9
    affected: no fix available “Fix deferred”
  • Red Hat Multicluster Engine for Kubernetes multicluster-engine/console-mce-rhel9
    affected: no fix planned “Out of support scope”
  • Red Hat Network Observability Operator network-observability/network-observability-console-plugin-rhel9, network-observability/network-observability-console-plugin-pf4-rhel9, network-observability/network-observability-console-plugin-pf5-rhel9
    affected: no fix available “Fix deferred”
  • 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
    affected: no fix planned “Out of support scope”
  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-agentic-console-rhel9, openshift-lightspeed/lightspeed-console-plugin-419-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9
    affected: no fix available “Fix deferred”
  • 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
    affected: no fix available, no fix planned “Out of support scope”
  • 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 amq-broker-bin.zip 7.14.1.CR3, amq-broker-maven-repository.zip 7.14.1.CR3
    affected: no fix available “Fix deferred”
  • Red Hat Ansible Automation Platform 2 automation-controller 4.5.37-1.el8ap, automation-platform-ui 2.6.15-1.el9ap, automation-gateway 2.5.20260923-1.el9ap, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9, ansible-automation-platform-24/lightspeed-rhel8, +1 more
    affected: no fix available, no fix planned “Out of support scope”
show 6 more
  • Red Hat build of Apache Camel for Spring Boot 4 rhaf-camel-spring-boot-maven-repository.zip 4.18.4.CS6, rhaf-camel-for-springboot-maven-repository.zip 3.5.16.CS2 Red Hat Build of Keycloak rhbk-quarkus-dist.zip 26.6.7.CR1, keycloak-operator.redhat-00001.zip 26.6.6, keycloak-operator.redhat-00003.zip 26.6.7 Red Hat Ceph Storage 9 rhceph/alloy-rhel10 Red Hat Connectivity Link 1 rhcl-1/rhcl-console-plugin-rhel9, rhcl-1/rhcl-rhdh-dynamic-plugin-rhel9 Red Hat Data Grid 8 redhat-datagrid-maven-repository.zip 8.6.1.CR1 Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9
    +4 more products
    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 9 grafana, grafana-selinux, grafana 10.2.6-28.el10_2.9 Red Hat Enterprise Linux 10 grafana-pcp 6.1.0-1.el10, grafana 10.2.6-28.el10_2.9
    affected: no fix available “Fix deferred”
  • Red Hat Hardened Images grafana13.1 13.1.8-0.5.hum1
    affected: no fix available
  • Red Hat JBoss Enterprise Application Platform 8 jboss-eap-runtime-maven-repository.zip 8.1.2, jboss-eap.1-runtime-maven-repository.zip 8.1.0 Red Hat JBoss Enterprise Application Platform Expansion Pack jboss-eap-runtime-maven-repository.zip 8.1.2, jboss-eap.1-runtime-maven-repository.zip 8.1.0 Red Hat OpenShift AI (RHOAI) rhoai/odh-workbench-codeserver-datascience-cpu-py312-rhel9 Red Hat OpenShift Container Platform 4 openshift4/ose-console, openshift4/ose-console-rhel9, openshift4/ose-monitoring-plugin-rhel8, openshift4/ose-monitoring-plugin-rhel9, openshift4/nmstate-console-plugin-rhel9, openshift4/ose-agent-installer-ui-rhel9, +1 more 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, openshift5/ose-networking-console-plugin-rhel9 Red Hat Openshift Data Foundation 4 odf4/odf-console-rhel9, odf4/ocs-client-console-rhel9, odf4/odf-multicluster-console-rhel9
    affected: no fix available “Fix deferred”
  • Red Hat OpenShift Virtualization 4 container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Secrets Management Console for Red Hat OpenShift external-secrets-management/console-plugin-rhel9
    affected: no fix planned “Out of support scope”
  • Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal
    affected: no fix available “Fix deferred”
  • Red Hat Hardened Images grafana13.2 13.2.4-0.4.hum1, grafana12.4 12.4.13-0.5.hum1
    not affected: vulnerable code not present

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
no
Technical impact
partial
Assessed
4 d ago

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/i18next/i18next/security/advisories/GHSA-6jcc-5g8w-32mx referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H

Affected products

  • i18next i18next

Classification

Weakness
  • CWE-471 Modification of Assumed-Immutable Data (MAID)
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

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.