RCE via Prototype Pollution in OpenSearch Dashboards (CVE-2026-18420) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-18420

RCE via Prototype Pollution in OpenSearch Dashboards

Answer in brief

CVE-2026-18420 records a Unknown severity vulnerability in RCE via Prototype Pollution in OpenSearch Dashboards. The current sources do not mark it as known exploited. The current feed maps AWS/Amazon OpenSearch Service (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 Aug 20, 2026Updated Aug 20, 2026Source checked Aug 20, 2026First seen by HOL Aug 20, 2026Material review Aug 20, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. 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 AWS/Amazon OpenSearch Service (generic), OpenSearch/OpenSearch Dashboards (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
AWS/Amazon OpenSearch Servicegeneric	>=3.0.0 <3.8.0	3.8.0
OpenSearch/OpenSearch Dashboardsgeneric	>=3.0.0 <3.8.0	3.8.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for AWS/Amazon OpenSearch Service, OpenSearch/OpenSearch Dashboards.
Review the reported fix. Update AWS/Amazon OpenSearch Service to 3.8.0; OpenSearch/OpenSearch Dashboards to 3.8.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 20, 2026

Sources and claim methodology

Upstream source description

Improper input validation in the Time Series Visual Builder (TSVB) plugin in OpenSearch Dashboards allows an authenticated remote user to execute arbitrary code on the server via a crafted JSON payload to the metrics visualization API endpoint. This issue is a form of prototype pollution that enables remote code execution. To remediate this issue, users should upgrade to OpenSearch Dashboards 3.8 or later.

Quoted source text, attributed separately from HOL analysis.