Deserialization in Microsoft Exchange Server 2013 Cumulative Update 23
CVE-2023-21529
Microsoft Exchange Server Remote Code Execution Vulnerability
Vulnerability class: Insecure Deserialization
EPSS: 0.276 (96.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.8 (High). 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.
Affected products
- Microsoft Exchange Server 2013 Cumulative Update 23 — versions 15.00.0
- Microsoft Exchange Server 2016 Cumulative Update 23 — versions 15.01.0
- Microsoft Exchange Server 2019 Cumulative Update 11 — versions 15.02.0
- Microsoft Exchange Server 2019 Cumulative Update 12 — versions 15.02.0
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
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.
Known ransomware campaign use: yes.
Public proof-of-concept exploits
References
- Microsoft Exchange Server Remote Code Execution Vulnerability (vendor-advisory)
Frequently asked questions
- What is CVE-2023-21529?
- CVE-2023-21529 is a high-severity vulnerability in Microsoft Exchange Server 2013 Cumulative Update 23, classified under Deserialization of Untrusted Data. CVSS score: 8.8/10. Published 2023-02-14.
- How severe is CVE-2023-21529?
- High severity. CVSS v3 base score is 8.8 out of 10.
- Is CVE-2023-21529 known to be exploited?
- Yes. CVE-2023-21529 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-13), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.