CVE-2026-18420
Authenticated RCE via TSVB metrics API in OpenSearch Dashboards (prototype pollution).
Is CVE-2026-18420 being exploited?
Not confirmed. CVE-2026-18420 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.66% probability of exploitation in the next 30 days.
How severe is CVE-2026-18420?
CVE-2026-18420 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-18420?
Yes. A fix has been recorded for CVE-2026-18420. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-18420 affect?
CVE-2026-18420 affects OpenSearch Dashboards < 3.8, Time Series Visual Builder (TSVB) plugin, Metrics visualization API endpoint. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-18420?
Upgrade OpenSearch Dashboards to 3.8 or later immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated remote attacker can achieve remote code execution on the Dashboards server via a crafted JSON payload to the TSVB metrics API (prototype pollution).
Immediate action required
- affected>= 3.0.0 and < 3.8.0
- affected>= 3.0.0 and < 3.8.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.