High severity · published Sep 8, 2026
CVE-2026-69378
Microsoft Exchange Server Denial of Service Vulnerability
7.5
CVSS
1.2%
EPSS
No
On KEV
Description
Uncontrolled recursion in Microsoft Exchange Server allows an unauthorized attacker to deny service over a network.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 67% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ES
Exchange Server · Microsoft
2016; 2019; 2019 · source: NVD
ME
Microsoft Exchange Server 2016 Cumulative Update 23 · Microsoft
15.01.0.0 before 15.01.2507.073 · source: vendor
ME
Microsoft Exchange Server 2019 Cumulative Update 14 · Microsoft
15.02.0.0 before 15.02.1544.046 · source: vendor
ME
Microsoft Exchange Server 2019 Cumulative Update 15 · Microsoft
15.02.0.0 before 15.02.1748.051 · source: vendor
ME
Microsoft Exchange Server Subscription Edition RTM · Microsoft
15.02.0.0 before 15.02.2562.049 · source: vendor
ES
Exchange Server Subscription Edition · Microsoft
before 15.02.2562.049 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-69378
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-69378
vendor-advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69378
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