---
id: "CVE-2026-118249"
kind: "vulnerability"
aliases: ["CVE-2026-118249", "GHSA-gfvx-2c2g-38wq"]
title: "Highcharts: series column construction writes to Object.prototype"
severity: "high"
cvss: 7.2
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "highcharts", "fixed": ["13.1.0"], "affected": ">= 13.0.0, <= 13.0.2", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["cwe-1321", "frontend", "highcharts", "javascript", "package", "web"]
not_affected_if: ["fixed-data-only", "version-13.1.0-or-later", "version-before-13.0.0"]
published_at: "2026-10-28T18:17:16+00:00"
first_seen_at: "2026-10-28T18:34:34+00:00"
updated_at: "2026-10-28T19:56:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118249", "first_seen_at": "2026-10-28T18:34:34+00:00"}, {"source": "ghsa", "url": "https://github.com/advisories/GHSA-gfvx-2c2g-38wq", "first_seen_at": "2026-10-28T19:56:29+00:00"}]
---

# Highcharts: series column construction writes to Object.prototype

Highcharts JS builds series data columns using point option keys directly as IDs, so crafted __proto__ or constructor keys in parsed chart data can write to Object.prototype. The polluted values then affect reads and for-in loops across the page, disrupting rendering or application logic when a chart is rendered.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- npm:highcharts affected >= 13.0.0, <= 13.0.2 fixed 13.1.0

## How to check

- Run `npm ls highcharts` or inspect the lockfile to find the installed Highcharts version.
- Search the project for `from 'highcharts'` or `require('highcharts')` to confirm the library is used in a page that renders chart data from parsed input.

## Fix

- Upgrade highcharts to `13.1.0` or later.

## Timeline

- 2026-10-28T18:34:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118249
- 2026-10-28T19:56:29+00:00 ghsa https://github.com/advisories/GHSA-gfvx-2c2g-38wq

## From the sources

### Impact
When series columns are built from point objects, the point option keys are used directly as data column ids, so the write that populates a column reaches `Object.prototype` and the `Object` constructor. Keys named `__proto__` and `constructor` survive `JSON.parse` as own enumerable properties, so an attacker who controls the point objects can set integer-keyed properties on `Object.prototype`, one per point index, to values of their choosing. Named properties cannot be reached this way. The integer keys still affect every object in the page: reading an out-of-range index on any array or plain object returns the attacker's value, and `for...in` over any object yields the injected keys, so unrelated code can take branches it should not using attacker-supplied data, and rendering can fail as a side effect. The properties remain in place once the chart has been built, and no user interaction is required beyond rendering the chart.

Consequences beyond disruption depend on the consuming application.

### Workarounds
Drop-in fix - for any versions affected (6.1.0-13.0.2).
Add the below IIFE to run after Highcharts is loaded.

```javascript
;!function(t){if(t&&t.Point&&!t.Point.prototype.protoPollutionPatched){var o=t.Point.prototype,r=o.optionsToObject,e=o.setNestedProperty,n=Object.prototype.hasOwnProperty;o.optionsToObject=function(t){if(t&&"object"==typeof t&&!Array.isArray(t)&&(n.call(t,"__proto__")||n.call(t,"constructor"))){var o={};for(var e in t)n.call(t,e)&&!c(e)&&(o[e]=t[e]);t=o}return r.call(this,t)},o.setNestedProperty=function(t,o,r){return String(r).split(".").some(c)?t:e.call(this,t,o,r)},o.protoPollutionPatched=!0}function c(t){return"__proto__"===t||"constructor"===t}}(Highcharts);
```

[Live demo & testing](https://jsfiddle.net/BlackLabel/nopc6vhj/)

### Obtaining the patched version
The patched releases are available from all the usual distribution channels. With npm, upgrade the affected package to the patched version listed above, for example `npm install highcharts@13.1.0`. If you load Highcharts from the CDN, use the versioned URLs on code.highcharts.com, for example `https://code.highcharts.com/13.1.0/highcharts.js`. For more on each installation method, see the [installation guide](https://www.highcharts.com/docs/getting-started/installation).

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_