Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability

HIGH 8.8EXPLOITED (CISA KEV)CVE-2023-21529 · Published 14/02/2023 · updated 19/08/2026

Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability. Actively exploited: CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on 13/04/2026. Patch affected systems as an emergency. It is known to be used in ransomware campaigns.

Package	Affected versions	Patched versions
exchange server microsoft	`= 2013= 2016= 2019`	No fix yet

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 · Patch
cisa.gov/known-exploited-vulnerabilities-catalog · US Government Resource
microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations · Technical Description
CISA KEV · CVE-2023-21529

Running one of these products? Scan your site to see whether it exposes a vulnerable version.

Scan my site free