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CVE-2026

Api.Msrc.Microsoft September 8, 2026

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Released: Sep 8, 2026

Please see Common Vulnerability Scoring System for more information on the definition of these metrics.

Missing authorization in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

The following table provides an exploitability assessment for this vulnerability at the time of original publication.

How could an attacker exploit this vulnerability?

An attacker with a low-privilege user account and an assigned mailbox, could exploit weaknesses in how Exchange validates requests and identity tokens to impersonate another user. By doing so, the attacker could then access mailboxes through Exchange services as if they were that user.

What privileges could be gained by an attacker who successfully exploited the vulnerability?

The attacker would be able to take over the mailboxes of all Exchange users, attackers can send emails, read emails, download attachments.

Younggi Park (grill66) with UIUC

Jongseong Kim (nevul37) with UIUC

Hwiwon Lee (hwiwonl) with UIUC

DongJun Kim (smlijun) with UIUC

To determine the support lifecycle for your software, see the Microsoft Support Lifecycle .

Information published.

Extracted Entities

Attack Types (1)