Medium · CVSS 5.3CVE-2026-118243

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

Answer in brief

CVE-2026-118243 records a Medium severity (CVSS 5.3) vulnerability in Highcharts Dashboards: `__proto__` data table id writes sync listeners to `Object.prototype`. The current sources do not mark it as known exploited. The current feed maps highcharts/highcharts (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 28, 2026Updated Oct 28, 2026Source checked Oct 28, 2026First seen by HOL Oct 28, 2026Material review Oct 28, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps highcharts/highcharts (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
highcharts/highchartsgeneric	>=1.0.0 <4.2.2	4.2.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for highcharts/highcharts.
Review the reported fix. Update highcharts/highcharts to 4.2.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 28, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.