Microsoft Exchange Server
CVE-2021-1730 — Microsoft Exchange Server Spoofing Vulnerability
Executive Summary
A spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user. This update addresses this vulnerability. To prevent these types of attacks, Microsoft recommends customers to download inline images from different DNSdomains than the rest of OWA. Please see further instructions in the FAQ to put in place this mitigations.
Overview
5.4
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
Required
SCOPE
Unchanged
Temporal Score: 4.9
EPSS Score
0.01817
probability of exploitation in the next 30 days
0.75903 percentile - updated 2026-06-20
View on FIRST.org
Affected Products
2 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Microsoft Exchange Server 2016 Cumulative Update 18 | 4571788 (Security Update) |
Important | Spoofing | Maybe |
| Microsoft Exchange Server 2019 Cumulative Update 7 | 4571787 (Security Update) |
Important | Spoofing | Maybe |
Patches
2 patches
| Article | Type | Restart |
|---|---|---|
4571788 |
Security Update | Maybe |
4571787 |
Security Update | Maybe |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
Mohamed Sayed of IBM X-Force
References
On This Page