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Fencer Intel
medium 6.1

CVE-2026-59710 json

showdown - Stored XSS via Unescaped Table Header ID Attribute Injection

published 4mo ago modified 2mo ago also EUVD-2026-41954 , GHSA-22g5-r2x5-97cx

cvss
6.1
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 27%
public exploits
0
none known

Summary

showdown contains a stored cross-site scripting vulnerability in the parseHeaders function of src/subParsers/makehtml/tables.js that fails to properly escape table header ID attributes. Attackers can inject arbitrary HTML and script-executing SVG elements through double-quote characters in markdown table headers, achieving stored XSS when untrusted markdown is rendered with the default github flavor configuration.

Patch / fix

Is CVE-2026-59710 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2026-59710 updated cvss 6.1

showdown: Showdown: Stored Cross-Site Scripting via unescaped table header ID attributes in markdown

  • Red Hat Cryostat 4 showdown 2.1.0, cryostat-openshift-console-plugin-npm Red Hat Multicluster Engine for Kubernetes multicluster-engine/console-mce-rhel9 Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-rhel9-operator, workload-availability/node-healthcheck-operator-bundle, workload-availability/node-healthcheck-must-gather-rhel9 Red Hat 3scale API Management Platform 2 3scale-amp2/system-rhel7 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/console-rhel9 Red Hat Ansible Automation Platform 2 automation-gateway 2.5.20260422-3.el9ap, automation-eda-controller 1.0.11-1.el9ap
    +4 more products
    Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-maas-rhel9, rhoai/odh-mod-arch-automl-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-mlflow-rhel9, +3 more Red Hat OpenShift Container Platform 4 openshift4/ose-console, openshift4/ose-console-rhel9, openshift4/ose-monitoring-plugin-rhel8 Red Hat OpenShift Virtualization 4 container-native-virtualization/kubevirt-console-plugin, container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Quay 3 quay/quay-rhel8, quay/quay-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

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/showdownjs/showdown/issues/1046 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA 4.0 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
npm showdown
<=2.1.0
 no fix listed

Affected products

  • showdown showdown

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

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.

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