CVE

CVE-2023-21529

P1⬤ KNOWN RANSOMWARE USE

Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability

Microsoft · Exchange Server

Date added (CISA)

2026-04-13

Remediation due

2026-04-27

Known ransomware use

Yes

Remediation priority

P1 — known ransomware use · past CISA due date

ATT&CK mapping

No ATT&CK mapping yet

The CTID Mappings Explorer hasn't published an exploitation/impact technique mapping for this CVE yet.