Actively exploited · Published Feb 14, 2023 · Assigned by microsoft
CVE-2023-21529Microsoft Exchange Server Remote Code Execution Vulnerability
High 8.8 Exploited Ransomware
In plain English
A high-severity unsafe deserialization in Microsoft Exchange Server 2013 Cumulative Update 23 from Microsoft. Attackers are actively exploiting it in the wild (listed by CISA on April 13, 2026). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 59.3% (higher than 99.1% of all known vulnerabilities). Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Federal agencies must remediate by Apr 27, 2026.
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 – before 15.00.1497.047 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 23 | 15.01.0 – before 15.01.2507.021 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 11 | 15.02.0 – before 15.02.0986.041 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 12 | 15.02.0 – before 15.02.1118.025 |
Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
References
- Microsoft Exchange Server Remote Code Execution Vulnerability vendor-advisory, patch
- 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/ vendor-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529 government-resource