CVE-2021-1730
<p>A spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.</p> <p>This update addresses this vulnerability.</p> <p>To prevent these types of attacks,…
Does this matter?
Lower severity and a low EPSS score (1.82%). Track it; it rarely justifies an emergency change on its own.
Description
<p>A spoofing vulnerability exists in Microsoft Exchange Server which could result in an attack that would allow a malicious actor to impersonate the user.</p> <p>This update addresses this vulnerability.</p> <p>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.</p>
- CVSS 3.1
- 5.4 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
- EPSS
- 1.82% probability · 79th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- microsoft/exchange server
- Source
- secure@microsoft.com
EPSS 1.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1730Patch, Vendor Advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1730Patch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.