Review reviewHigh

CVE-2026-23666

Microsoft Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5 AND 4.7.2, Microsoft .NET Framework 3.5 AND 4.8

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

PRIORITY ASSESSMENT

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability1.33%

Technical severityCVSS 7.5

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

Product: Microsoft Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5 AND 4.7.2, Microsoft .NET Framework 3.5 AND 4.8
Affected versions: >= 3.5.0 < 2.0.50727.8982 & 3.0.30729.8976, >= 4.7.0 < 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0, >= 4.8.0 < 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0, >= 4.8.1 < 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0, >= 4.7.0 < 4.8.4801.0, >= 4.8.0 < 4.8.4801.0, 3.5, 4.7.2, 4.8, 4.8.1, 4.6.2, 4.7, 4.7.1
Fixed versions: No verified fixed-version field is available yet

Confirm exposure before applying a vendor-supported change.

1
Identify
Confirm that Microsoft Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5 AND 4.7.2, Microsoft .NET Framework 3.5 AND 4.8 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.