# CVE-2026-118243: Highcharts Dashboards: `__proto__` data table id writes sync listeners to `Object.prototype`

Status: published. Published: 2026-10-28. Updated: 2026-11-02.

Highcharts JS is a JavaScript charting library based on SVG. From 1.0.0 until 4.2.2, Highcharts Dashboards stores DataCursor listener and state maps in plain objects keyed by DataTable ID. A __proto__ table ID supplied through dataPool connector configuration resolves to Object.prototype, and sync registration creates an enumerable property there whose suffix can be influenced through the sync group option. The property is visible on every object, and lasting sync states can throw and stop features such as extremes synchronization. Exploitation requires untrusted dashboard configuration and an enabled component sync, but no user interaction beyond loading the board. This issue is fixed in 4.2.2.

## Remediation

- fix: @highcharts/dashboards (npm): OSV reports a fixed version 4.2.2. Check the advisory for supported release branches. (source: OSV GHSA-jqgh-w3cc-7jqw) — https://github.com/advisories/GHSA-jqgh-w3cc-7jqw

## Affected products and versions

- highcharts / highcharts: >= 1.0.0, < 4.2.2 (affected). Source: CNA: GitHub_M
-  / @highcharts/dashboards (@highcharts/dashboards): ≥ 1.0.0; < 4.2.2 (affected, semver); OSV events: introduced 1.0.0; fixed 4.2.2. Source: OSV GHSA-jqgh-w3cc-7jqw

## Severity and prioritization

- CVSS 4.0: 5.3 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:L/SI:L/SA:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.35% as of 2026-11-02; percentile 28.79%

- SSVC: exploitation none; automatable yes; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-1321

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/highcharts/highcharts/security/advisories/GHSA-jqgh-w3cc-7jqw (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/highcharts/highcharts/commit/ade5a41a700212f09133223ca990a3737d1d9ec6 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/highcharts/highcharts/releases/tag/dashboards-v4.2.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-jqgh-w3cc-7jqw (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-jqgh-w3cc-7jqw (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118243; retrieved 2026-11-02; source updated 2026-11-02

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-jqgh-w3cc-7jqw; retrieved 2026-11-02; source updated 2026-10-28

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118243; retrieved 2026-11-02; source updated Not reported

Revision: 17e10465d15d3842bca914eb7596c431a75e5b6570be9ac1af66f5aa6dbe7258

Canonical: https://y2.dev/cve/CVE-2026-118243

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