What is CVE-2026-70279?

CVE-2026-70279 is a critical-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2026-10-13.

How severe is CVE-2026-70279?

Critical severity. CVSS v3 base score is 9.3 out of 10.

XSS in Microsoft Exchange Server 2016 Cumulative Update 23

CVE-2026-70279

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Vulnerability class: XSS (Cross-Site Scripting)

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

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.

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-79 — Cross-site Scripting

References

Microsoft Exchange Server Spoofing Vulnerability (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-70279?: CVE-2026-70279 is a critical-severity vulnerability in Microsoft Exchange Server 2016 Cumulative Update 23, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2026-10-13.
How severe is CVE-2026-70279?: Critical severity. CVSS v3 base score is 9.3 out of 10.