What is CVE-2026-69356?

CVE-2026-69356 is a critical-severity vulnerability in Microsoft Exchange Server, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2026-09-08.

How severe is CVE-2026-69356?

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

XSS in Microsoft Exchange Server

CVE-2026-69356

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 2026-09-08 · last modified 2026-09-30.

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

EPSS: 0.008 (54.7th percentile), scored 2026-10-24.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 55th percentile — 54.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: -0.000

Affected products

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

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

Frequently asked questions

What is CVE-2026-69356?: CVE-2026-69356 is a critical-severity vulnerability in Microsoft Exchange Server, classified under Cross-site Scripting. CVSS score: 9.3/10. Published 2026-09-08.
How severe is CVE-2026-69356?: Critical severity. CVSS v3 base score is 9.3 out of 10.