CVE-2026-18420: Prototype Pollution (CVSS 8.8)

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.

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CVSS v3.1 Score

8.8

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0066

Probability of exploitation

0.50%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-1321 CWE-1321

References

Other 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

Frequently Asked Questions

What is CVE-2026-18420? +

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. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-18420? +

CVE-2026-18420 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0066, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-18420? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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