Microsoft · Exchange Server
CVE-2023-21529
Microsoft Exchange Server Remote Code Execution Vulnerability
Exploited in attacks
Used by ransomware
High 8.8 Attack chance: 59%
What it is
Microsoft Exchange Server Remote Code Execution Vulnerability
CISA: Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: April 27, 2026
More exploited flaws from Microsoft
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Aug 21, 2024 | Information Disclosure | Exchange Server | High 7.2 | 54% |
| Feb 15, 2024 | Privilege Escalation | Exchange Server | Critical 9.8 | 13% |
| Jan 10, 2023 | Privilege Escalation | Exchange Server | High 8.8 | 77% |
| Sep 30, 2022 | Server-Side Request Forgery | Exchange Server | High 8.8 | >99.9% |
| Sep 30, 2022 | Remote Code Execution | Exchange Server | High 8.0 | >99.9% |
| Mar 3, 2022 | Privilege Escalation | Exchange Server | High 7.4 | 27% |
| Jan 18, 2022 | Information Disclosure | Exchange Server | High 7.3 | 98% |
| Nov 3, 2021 | Validation Key Remote Code Execution | Exchange Server | High 8.8 | >99.9% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.