CVE-2023-21529
High 8.8 Exploited in the wild (KEV) Used in ransomware campaigns
Confirmed active exploitation — CISA KEV catalog
- Name
- Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
- Added to catalog
- Remediation due date (US federal)
- 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.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Metrics
- CVSS 3.1
-
8.8 (HIGH)
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 59% (percentile: 99) as of 2 November 2026
- CWE
- CWE-502
Affected products
microsoft: exchange server
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 PatchVendor Advisory
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 PatchVendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023… US Government Resource
- https://www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaz… Technical Description