High 7.5Published Apr 14, 2026

CVE-2026-23666.NET Framework Denial of Service Vulnerability

Updated under an hour ago (Oct 27, 2026, 7:50 AM ET)

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It affects Microsoft .NET Framework 3.5 and 8 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Microsoft .NET Framework 3.5

Exploited in the last 30 days

Improper input validation in .NET Framework allows an unauthorized attacker to deny service over a network.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
Weakness (CWE): CWE-755, CWE-366
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: microsoft
NVD analysis: Modified
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Microsoft Microsoft .NET Framework 3.5 microsoft:net_framework_3.5 (from the name)	3.5.0 builds before 2.0.50727.8982 & 3.0.30729.8976	CNA record
Microsoft Microsoft .NET Framework 3.5 AND 4.7.2 microsoft:net_framework_3.5_and_4.7.2 (from the name)	4.7.0 builds before 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0	CNA record
Microsoft Microsoft .NET Framework 3.5 AND 4.8 microsoft:net_framework_3.5_and_4.8 (from the name)	4.8.0 builds before 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0	CNA record
Microsoft Microsoft .NET Framework 3.5 AND 4.8.1 microsoft:net_framework_3.5_and_4.8.1 (from the name)	4.8.1 builds before 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0	CNA record
Microsoft Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 microsoft:net_framework_4.6.2_4.7_4.7.1_4.7.2 (from the name)	from 4.7.0 before 4.8.4801.0	CNA record
Microsoft Microsoft .NET Framework 4.8 microsoft:net_framework_4.8 (from the name)	from 4.8.0 before 4.8.4801.0	CNA record
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux	10	CISA ADP
Red Hat Red Hat Hardened Images redhat:hummingbird	1	CISA ADP
microsoft .net_framework microsoft:.net_framework	3.5; 3.5; 4.7.2; 3.5; 4.8; 3.5; 4.8.1; 4.6.2; and 4 more ranges	NVD

References

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666	vendor-advisory, patch
https://access.redhat.com/security/cve/CVE-2026-23666
https://bugzilla.redhat.com/show_bug.cgi?id=2458271
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23666.json

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.