What is CVE-2026-63509?

CVE-2026-63509 is a critical-severity vulnerability in Microsoft Fabric, classified under Relative Path Traversal. CVSS score: 9.9/10. Published 2026-08-20.

How severe is CVE-2026-63509?

Critical severity. CVSS v3 base score is 9.9 out of 10.

Path Traversal in Microsoft Fabric

CVE-2026-63509

Relative path traversal in Microsoft Fabric allows an authorized attacker to elevate privileges over a network.

Published 2026-08-20 · last modified 2026-09-04.

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.010 (62.3th percentile), scored 2026-10-06.

Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 62.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.010 · change: +0.004

Affected products

Weakness classification (CWE)

CWE-23 — Relative Path Traversal

References

Microsoft Fabric Elevation of Privilege Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-63509?: CVE-2026-63509 is a critical-severity vulnerability in Microsoft Fabric, classified under Relative Path Traversal. CVSS score: 9.9/10. Published 2026-08-20.
How severe is CVE-2026-63509?: Critical severity. CVSS v3 base score is 9.9 out of 10.