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CVE-2026-18420: RCE via Prototype Pollution in OpenSearch Dashboards

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-20 · updated 2026-10-26
• Weakness: CWE-1321

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.

Affected products

• AWS Amazon OpenSearch Service: from 3.0.0 before 3.8.0 — fixed in 3.8.0
• OpenSearch Dashboards: from 3.0.0 before 3.8.0 — fixed in 3.8.0

How to fix

Upgrade to a fixed version: AWS Amazon OpenSearch Service 3.8.0; OpenSearch Dashboards 3.8.0. Check the vendor advisory for mitigations.

References

• https://aws.amazon.com/security/security-bulletins/2026-085-aws/
• https://github.com/opensearch-project/OpenSearch-Dashboards/releases/tag/3.8.0
• https://github.com/opensearch-project/OpenSearch-Dashboards/security/advisories/GHSA-xmqx-xq2p-8jq2

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