High severity · published Apr 14, 2026
CVE-2026-23666
.NET Framework Denial of Service Vulnerability
7.5
CVSS
1.3%
EPSS
No
On KEV
Description
Improper input validation in .NET Framework 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)1.3% · higher than 71% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MN
Microsoft .NET Framework 3.5 · Microsoft
3.5.0 before 2.0.50727.8982 & 3.0.30729.8976 · source: vendor
MN
Microsoft .NET Framework 3.5 AND 4.7.2 · Microsoft
4.7.0 before 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0 · source: vendor
MN
Microsoft .NET Framework 3.5 AND 4.8 · Microsoft
4.8.0 before 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0 · source: vendor
MN
Microsoft .NET Framework 3.5 AND 4.8.1 · Microsoft
4.8.1 before 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0 · source: vendor
MN
Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 · Microsoft
4.7.0 before 4.8.4801.0 · source: vendor
MN
Microsoft .NET Framework 4.8 · Microsoft
4.8.0 before 4.8.4801.0 · source: vendor
NF
.net Framework · Microsoft
3.5; 3.5; 4.7.2; 3.5; 4.8; 3.5; +6 more · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-23666
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-23666
Vendor Advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-23666
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2458271
security.access.redhat.com
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23666.json
More from Microsoft .NET Framework 3.5
9.8
CVE-2020-0646
Microsoft .NET Framework Remote Code Execution Vulnerability
7.8
CVE-2020-1147
Microsoft .NET Framework, SharePoint, and Visual Studio Remote Code Execution Vulnerability
7.5
CVE-2024-29059
.NET Framework Information Disclosure Vulnerability
9.8
CVE-2026-47304
.NET Security Feature Bypass Vulnerability
8.8
CVE-2026-85363
.NET Framework Elevation of Privilege Vulnerability