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Fencer Intel
low 3.7

CVE-2026-126066 json

fast-xml-parser: Quadratic CPU consumption scanning unterminated stop-node tags

published 8d ago modified yesterday also EUVD-2026-122845 , GHSA-474x-hrwr-fgx4

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Prior to 5.12.0, when the non-default stopNodes option is enabled, readStopNodeData() in OrderedObjParser.js calls readTagExp() for each less-than character in an unterminated stop-node body and repeatedly rescans the remaining input while looking for a closing greater-than character. An attacker who supplies XML containing many tag fragments without a later closing character can cause quadratic rescanning before parsing fails, blocking a Node.js event loop and causing CPU-exhaustion denial of service. This issue is fixed in version 5.12.0.

Patch / fix

  • npm fast-xml-parser 5.12.0

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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-2026-126066 updated cvss 3.7

fast-xml-parser: fast-xml-parser: Denial of Service via quadratic rescanning of unterminated tags

  • Red Hat Cryostat 4 cryostat/cryostat-openshift-console-plugin-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-ui-rhel9 Red Hat OpenShift Serverless openshift-serverless-1/logic-rhel9-operator Red Hat Advanced Cluster Security 4 advanced-cluster-security/rhacs-main-rhel8, advanced-cluster-security/rhacs-main-rhel9 Red Hat Advanced Cluster Security 5 advanced-cluster-security/rhacs-main-rhel9 Red Hat Connectivity Link 1 rhcl-1/rhcl-rhdh-dynamic-plugin-rhel9
    +4 more products
    Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9, rhdh/red-hat-developer-hub-backstage-plugin-orchestrator, rhdh/red-hat-developer-hub-backstage-plugin-lightspeed-backend, rhdh/red-hat-developer-hub-backstage-plugin-orchestrator-backend, rhdh/red-hat-developer-hub-backstage-plugin-scaffolder-backend-module-orchestrator Red Hat Developer Hub 2 rhdh/rhdh-hub-rhel10, rhdh/backstage-plugin-org, rhdh/backstage-plugin-techdocs, rhdh/backstage-plugin-kubernetes, rhdh/backstage-community-plugin-rbac, rhdh/backstage-plugin-techdocs-backend, +28 more Red Hat Openshift Data Foundation 4 odf4/mcg-core-rhel9, odf4/odf-console-rhel9, odf4/ocs-client-console-rhel9, odf4/odf-multicluster-console-rhel9 Red Hat OpenShift GitOps openshift-gitops-1/argocd-rhel9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenShift Virtualization 4 container-native-virtualization/kubevirt-console-plugin, container-native-virtualization/kubevirt-console-plugin-rhel9
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift Virtualization 5 container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal, ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available “Fix deferred”

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

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
GitHub 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
npm fast-xml-parser
<5.12.0
5.12.0

Affected products

  • NaturalIntelligence fast-xml-parser

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 NaturalIntelligence/fast-xml-parser published their own advisory on GitHub. Reviewed sources take precedence over it.