What is CVE-2018-8159?

CVE-2018-8159 is a medium-severity vulnerability in Microsoft Exchange Server, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2018-05-09.

How severe is CVE-2018-8159?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Microsoft Exchange Server

CVE-2018-8159

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests, aka "Microsoft Exchange Elevation of Privilege Vulnerability." This affects Microsoft Exchange Server.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2018-05-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.035 (89.0th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 89th percentile — 89.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.050 · newest: 0.035 · change: -0.015

Affected products

Microsoft Exchange Server — versions 2013, 2016
Microsoft Exchange Server — versions 2013 Cumulative Update 19, 2013 Cumulative Update 20, 2016 Cumulative Update 8

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8159 (Patch, Vendor Advisory)
www.securityfocus.com/bid/104056 (VDB Entry, Third Party Advisory, vdb-entry)
www.securitytracker.com/id/1040850 (VDB Entry, Third Party Advisory, vdb-entry)

Frequently asked questions

What is CVE-2018-8159?: CVE-2018-8159 is a medium-severity vulnerability in Microsoft Exchange Server, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2018-05-09.
How severe is CVE-2018-8159?: Medium severity. CVSS v3 base score is 5.4 out of 10.