ACTIVELY EXPLOITED
CVE-2023-21529: Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
| Vendor | Microsoft |
|---|---|
| Product | Exchange Server |
| Actively exploited | Yes |
| Added to CISA KEV | 13 Apr 2026 |
| CISA federal deadline | 27 Apr 2026 |
| Ransomware use | Known |
| Weakness (CWE) | CWE-502 |
Required action (CISA's text)
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 (NVD)
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
SOURCES
Other Microsoft flaws
- patchtuesday:2026-11: Vulnerability in Microsoft
- CVE-2026-124194: Microsoft Office Outlook Missing User Interaction for Potentially Unsafe Action Vulnerability
- CVE-2026-96951: Microsoft Windows Command Injection Vulnerability
- CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability
- CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability
Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.