What is CVE-2026-77910?

CVE-2026-77910 is a high-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under Incorrect Authorization. CVSS score: 8.8/10. Published 2026-10-13.

How severe is CVE-2026-77910?

High severity. CVSS v3 base score is 8.8 out of 10.

Auth bypass in Microsoft Exchange Server 2016 Cumulative Update 23

CVE-2026-77910

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

Vulnerability class: Broken Access Control

Published 2026-10-13 · last modified 2026-10-13.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77910 (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-77910?: CVE-2026-77910 is a high-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under Incorrect Authorization. CVSS score: 8.8/10. Published 2026-10-13.
How severe is CVE-2026-77910?: High severity. CVSS v3 base score is 8.8 out of 10.