Vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23
CVE-2026-21527
User interface (ui) misrepresentation of critical information in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
EPSS: 0.001 (21.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C.
Affected products
- Microsoft Exchange Server 2016 Cumulative Update 23 — versions 15.01.0.0
- Microsoft Exchange Server 2019 Cumulative Update 14 — versions 15.02.0.0
- Microsoft Exchange Server 2019 Cumulative Update 15 — versions 15.02.0.0
- Microsoft Exchange Server Subscription Edition Rtm — versions 15.02.0.0
Weakness classification (CWE)
References
- Microsoft Exchange Server Spoofing Vulnerability (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2026-21527?
- CVE-2026-21527 is a medium-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.5/10. Published 2026-02-10.
- How severe is CVE-2026-21527?
- Medium severity. CVSS v3 base score is 6.5 out of 10.