What is the CVSS score of CVE-2026-21527?

CVE-2026-21527 has a CVSS 3.1 base score of 6.5 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N. EPSS exploitation probability: 0.1%.

Which versions of Exchange Server are affected by CVE-2026-21527?

CVE-2026-21527 presents notable security risk rated CVSS 6.5. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2026-21527?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Exchange Server CVE-2026-21527

MEDIUM

Insufficient Verification of Data Authenticity (CWE-345)

2026-02-10 secure@microsoft.com

Microsoft Exchange Server Authentication Bypass

6.5

CVSS 3.1 · Vendor: microsoft

Severity by source

Vendor (microsoft) PRIMARY

6.5 MEDIUM

AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:02 vuln.today

CVE Published

Feb 10, 2026 - 18:16 nvd

MEDIUM 6.5

DescriptionCVE.org

User interface (ui) misrepresentation of critical information in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

AnalysisAI

Microsoft Exchange Server is vulnerable to UI spoofing attacks that allow unauthenticated remote attackers to misrepresent critical information and deceive users. The vulnerability has a CVSS score of 6.5 and currently lacks an available patch, leaving affected systems exposed to social engineering and impersonation attacks. Organizations running Exchange Server should implement network-level protections and monitor for suspicious activity until a fix is released.

Technical ContextAI

Classified as CWE-345 (Insufficient Verification of Data Authenticity). Affects Exchange Server. User interface (ui) misrepresentation of critical information in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.