CVE DATABASE / CVE-2023-21529
CVE-2023-21529
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
CVSS 8.8 · HIGH
⚠ CISA KEV — ACTIVELY EXPLOITED
RANSOMWARE
On the CISA KEV catalog
Confirmed exploited in the wild. Added 2026-04-13.
Federal remediation due 2026-04-27.
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.
Summary
Microsoft Exchange Server Remote Code Execution Vulnerability
CVSS 3.1 breakdown
| Base score | 8.8 (HIGH) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Attack vector | NETWORK |
| Attack complexity | LOW |
| Privileges required | LOW |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity | HIGH |
| Availability | HIGH |
Weakness type (CWE)
Affected products
Microsoft exchange server
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References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529
- 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/
Data: NIST NVD + CISA KEV. NVD last modified 2026-04-14. Always verify against the vendor advisory before acting.