April 13, 2026 · Applied Cybernetics Group
CVE-2023-21529 — Microsoft Exchange Server
known ransomware use
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
- Added to KEV
2026-04-13- Federal due date
2026-04-27- Vendor
- Microsoft
- Product
- Exchange Server
- EPSS
- 96.5th percentile (score 0.270, as of
2026-06-08) - NVD CVSS v3.1
- —
- Ransomware use
- Known
- Upstream
- https://nvd.nist.gov/vuln/detail/CVE-2023-21529
CISA short description
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.