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CVE-2026-21527 Microsoft CVE debrief

CVE-2026-21527 is a medium-severity vulnerability in Microsoft Exchange Server that allows an unauthorized attacker to perform spoofing over a network. The vulnerability has a CVSS score of 6.5 and was first published on 2026-02-10.

Vendor
Microsoft
Product
Exchange Server
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-02-10
Original CVE updated
2026-06-15
Advisory published
2026-02-10
Advisory updated
2026-06-15

Who should care

Administrators and users of Microsoft Exchange Server 2016, 2019, and Subscription Edition should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

The vulnerability is caused by a user interface (UI) misrepresentation of critical information in Microsoft Exchange Server. This allows an unauthorized attacker to perform spoofing over a network.

Defensive priority

MEDIUM

Recommended defensive actions

  • Apply patches or updates provided by Microsoft to fix the vulnerability.
  • Refer to [ref-4](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21527) for mitigation or vendor reference.

Evidence notes

The vulnerability is analyzed and has a CWE classification of CWE-345, CWE-451, and CWE-1286.

Official resources

CVE-2026-21527 was first published on 2026-02-10 and last modified on 2026-06-15.