CVE-2023-21529
HIGH severity · CVSS 8.8 · Insecure deserialization · actively exploited (CISA KEV)
8.8CVSS HIGH exploited ransomware
Actively exploited in the wild (CISA Known Exploited Vulnerabilities).
Known use in ransomware campaigns. Added to KEV 2026-04-13. US federal agencies must patch by 2026-04-27.
Summary
Microsoft Exchange Server Remote Code Execution Vulnerability
Impact & exploitability
Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionNone
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
Exploit probability (EPSS)62%
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected products we track (1)
Recommendation
This vulnerability is being actively exploited in the wild — patch affected products urgently. Open any affected product above for its exact safe version.
Official patch: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 ↗
Additional information
- NVD record
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529Patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529
- https://www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations/