CVE-2023-21529

HighActively exploited (CISA KEV)Known to be used in ransomware campaigns

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

SeverityHigh

CVSS8.8

Exploit probability—

Product

Microsoft Exchange Server

PublishedFeb 14, 2023

First seenFeb 14, 2023

Added to KEVApr 13, 2026

Weakness typeCWE-502Deserialization of untrusted data

How to fix

CISA 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.

CISA due date: Apr 27, 2026

Patches

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529

Vendor advisories

microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations/

Affected products

Product	Affected versions	Fixed in
microsoft exchange_server	2013, 2016, 2019	—

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