November 3, 2021 · Applied Cybernetics Group
CVE-2021-34523 — Microsoft Exchange Server
known ransomware use
Microsoft Exchange Server Privilege Escalation Vulnerability
- Added to KEV
2021-11-03- Federal due date
2021-11-17- Vendor
- Microsoft
- Product
- Exchange Server
- EPSS
- 100.0th percentile (score 1.000, as of
2026-09-16) - NVD CVSS v3.1
- 9 (CRITICAL)
- Ransomware use
- Known
- ATT&CK
- T1190 · signal rollup
- Upstream
- https://nvd.nist.gov/vuln/detail/CVE-2021-34523
CISA short description
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
Required action
Apply updates per vendor instructions.
NVD description
Microsoft Exchange Server Elevation of Privilege Vulnerability