CVE-2023-21529
Microsoft Exchange Server Remote Code Execution Vulnerability
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
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.
CISA notes
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 ; https://nvd.nist.gov/vuln/detail/CVE-2023-21529
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Severity
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CExploitation Context
as of October 14, 2026- CISA added CVE-2023-21529 to the KEV catalog 1,154 days after its CVE record was published. The median for entries added in 2026 so far is 15 days.
- It is one of 391 Microsoft entries in the CISA KEV catalog, and one of 40 added in 2026.
- Its current EPSS score (59.3%) is higher than that of 53% of CISA KEV entries.
Affected Products
| Vendor | Product | Affected versions |
|---|---|---|
| Microsoft | Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 | 15.00.0 to <15.00.1497.047 |
| Microsoft | Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 | 15.01.0 to <15.01.2507.021 |
| Microsoft | Microsoft Microsoft Exchange Server 2019 Cumulative Update 11 | 15.02.0 to <15.02.0986.041 |
| Microsoft | Microsoft Microsoft Exchange Server 2019 Cumulative Update 12 | 15.02.0 to <15.02.1118.025 |
References
1 LinksRecord Details
More from Microsoft
Microsoft Exchange Server Remote Code Execution Vulnerability
Microsoft Exchange Server Remote Code Execution Vulnerability
Microsoft Exchange Server Elevation of Privilege Vulnerability
Microsoft Exchange Server Remote Code Execution Vulnerability
Related
Tool categories
CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.