What is CVE-2026-66803?

CVE-2026-66803 is a critical-severity vulnerability in Microsoft Azure Cosmos Db, classified under Improper Access Control. CVSS score: 10.0/10. Published 2026-07-30.

How severe is CVE-2026-66803?

Critical severity. CVSS v3 base score is 10.0 out of 10.

Vulnerability in Microsoft Azure Cosmos Db

CVE-2026-66803

Improper access control in Azure Cosmos DB allows an unauthorized attacker to execute code over a network.

Published 2026-07-30 · last modified 2026-10-23.

CVSS v3 metric

CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.009 (59.7th percentile), scored 2026-11-03.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 59.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-284 — Improper Access Control

References

Azure Cosmos DB Remote Code Execution Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-66803?: CVE-2026-66803 is a critical-severity vulnerability in Microsoft Azure Cosmos Db, classified under Improper Access Control. CVSS score: 10.0/10. Published 2026-07-30.
How severe is CVE-2026-66803?: Critical severity. CVSS v3 base score is 10.0 out of 10.