High severity · published Dec 9, 2025
CVE-2025-64666
Improper input validation in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network
7.5
CVSS
1%
EPSS
No
On KEV
Description
Improper input validation in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.0% · higher than 63% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ES
Exchange Server · Microsoft
2016; 2016; 2016; 2016; 2016; 2016; +31 more · source: NVD
ES
Exchange Server Subscription Edition · Microsoft
before 15.02.2562.035 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-64666
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-64666
Vendor Advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-64666
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