Prototype Pollution in AWS Amazon Opensearch Service
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.
Vulnerability class: Prototype Pollution
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (50.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
Weakness classification (CWE)
References
- ff89ba41-3aa1-4d27-914a-91399e9639e5 (patch)
- ff89ba41-3aa1-4d27-914a-91399e9639e5 (third-party-advisory)
- ff89ba41-3aa1-4d27-914a-91399e9639e5 (vendor-advisory)
Frequently asked questions
- What is CVE-2026-18420?
- CVE-2026-18420 is a high-severity vulnerability in AWS Amazon Opensearch Service, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 8.8/10. Published 2026-08-20.
- How severe is CVE-2026-18420?
- High severity. CVSS v3 base score is 8.8 out of 10.