What is CVE-2023-21745?

CVE-2023-21745 is a high-severity vulnerability in Microsoft Exchange Server, classified under Deserialization of Untrusted Data. CVSS score: 8.0/10. Published 2023-01-10.

How severe is CVE-2023-21745?

High severity. CVSS v3 base score is 8.0 out of 10.

Deserialization in Microsoft Exchange Server

CVE-2023-21745

Microsoft Exchange Server Spoofing Vulnerability

Vulnerability class: Insecure Deserialization

Published 2023-01-10 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.015 (73.8th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 73.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.015 · newest: 0.015 · change: 0.000

Affected products

Microsoft Exchange Server — versions 2016, 2019
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)

CWE-502 — Deserialization of Untrusted Data

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21745 (vendor-advisory)

Frequently asked questions

What is CVE-2023-21745?: CVE-2023-21745 is a high-severity vulnerability in Microsoft Exchange Server, classified under Deserialization of Untrusted Data. CVSS score: 8.0/10. Published 2023-01-10.
How severe is CVE-2023-21745?: High severity. CVSS v3 base score is 8.0 out of 10.