CVE-2026-77910

Summary

Microsoft Exchange Server contains an authorization flaw that allows an authenticated attacker to escalate their privileges over a network, potentially leading to full system compromise. This vulnerability specifically affects how the server handles authorization checks for certain network operations.

Exploitability

Exploitation requires an initial authenticated session and is moderately difficult to achieve, as it involves crafting specific network requests that bypass authorization controls while maintaining active session state.

Blast radius

If exploited, this vulnerability could allow attackers to gain elevated privileges across the Exchange server, potentially enabling them to access sensitive email data, modify system configurations, or even take full control of the server environment.

Detection

Monitor for unusual authentication patterns in Exchange server logs, particularly around the /EWS/ and /RPC/ endpoints where the authorization bypass occurs, looking for repeated failed authorization attempts followed by successful elevated access requests.

Prioritized remediation

Apply the Microsoft Exchange Server cumulative update released in the July 2026 security updates, specifically version 15.00.1497.000 or later, which contains the fix for this authorization flaw.

Analysis generated locally by garnet-coder (no data left the box). AI-assisted — verify against primary sources before acting.