Medium · CVSS 8.7CVE-2026-84942

Stored Cross-Site Scripting via Vega Expression Function Bypass in OpenSearch DashboardsCVE-2026-84942

Answer in brief

CVE-2026-84942 records a Medium severity (CVSS 8.7) vulnerability in Stored Cross-Site Scripting via Vega Expression Function Bypass in OpenSearch Dashboards. The current sources do not mark it as known exploited. The current feed maps OpenSearch/OpenSearch Dashboards (generic), OpenSearch/OpenSearch Dashboards (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 Sep 8, 2026Updated Sep 9, 2026Source checked Oct 25, 2026First seen by HOL Sep 8, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Not reported

Why this deserves its current priority

CVSS is 8.7. 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 OpenSearch/OpenSearch Dashboards (generic), OpenSearch/OpenSearch Dashboards (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
OpenSearch/OpenSearch Dashboardsgeneric	v2.0.0	Not reported
OpenSearch/OpenSearch Dashboardsgeneric	>=v2.0.0 <=v3.5.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for OpenSearch/OpenSearch Dashboards, OpenSearch/OpenSearch Dashboards.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 8, 2026

Sources and claim methodology

Upstream source description

Improper input validation in the Vega expression function implementation in OpenSearch Dashboards allows a remote authenticated actor with dashboard write permissions to execute arbitrary JavaScript in the context of other users' browser sessions by saving a crafted Vega visualization. The checkForFunctionProperty validation routine failed to recurse into arrays of objects, allowing a function property nested inside an array to bypass validation.

Quoted source text, attributed separately from HOL analysis.