ACTIVELY EXPLOITED
CVE-2021-42321: Microsoft Exchange Server Remote Code Execution Vulnerability
| Vendor | Microsoft |
|---|---|
| Product | Exchange |
| Actively exploited | Yes |
| Added to CISA KEV | 17 Nov 2021 |
| CISA federal deadline | 1 Dec 2021 |
| Ransomware use | Known |
| Weakness (CWE) | CWE-184, CWE-502 |
Required action (CISA's text)
Apply updates per vendor instructions.
Description (NVD)
An authenticated attacker could leverage improper validation in cmdlet arguments within Microsoft Exchange and perform 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.