CVE-2020-0903 — A cross-site-scripting (XSS) vulnerability exists when Microsoft Exchange Server

A cross-site-scripting (XSS) vulnerability exists when Microsoft Exchange Server does not properly sanitize a specially crafted web request to an affected Exchange server, aka 'Microsoft Exchange Server Spoofing Vulnerability'.

01What is this vulnerability?

A cross-site-scripting (XSS) vulnerability exists when Microsoft Exchange Server does not properly sanitize a specially crafted web request to an affected Exchange server, aka 'Microsoft Exchange Server Spoofing Vulnerability'.

02Affected products

Vendor	Product	Versions
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 4	unspecified
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 15	unspecified
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 3	unspecified
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 14	unspecified

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-03-12T15:48:58.000Z
• Last modified: 2025-02-28T20:11:27.037Z

09References

• portal.msrc.microsoft.com — https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0903