How severe is CVE-2026-23666?

CVE-2026-23666 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-23666 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23666?

CVE-2026-23666 primarily affects Microsoft .net Framework. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-23666?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-23666 have an EU (EUVD) identifier?

Yes. CVE-2026-23666 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22363.

When was CVE-2026-23666 published?

CVE-2026-23666 was published on 2026-04-14 and last updated on 2026-06-30.

CVE-2026-23666

CVE-2026-23666 is a high-severity vulnerability in Microsoft .net Framework with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (68th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-22363
Weakness: CWE-755
Affected product: Microsoft .net Framework
Published: 2026-04-14
Last modified: 2026-06-30

Description

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

Frequently asked questions

What is CVE-2026-23666?: Improper input validation in .NET Framework allows an unauthorized attacker to deny service over a network.
How severe is CVE-2026-23666?: CVE-2026-23666 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-23666 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (68th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23666?: CVE-2026-23666 primarily affects Microsoft .net Framework. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-23666?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-23666 have an EU (EUVD) identifier?: Yes. CVE-2026-23666 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22363.
When was CVE-2026-23666 published?: CVE-2026-23666 was published on 2026-04-14 and last updated on 2026-06-30.

References

Affected products (7)

cpe:2.3:a:microsoft:.net_framework:3.5:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.7.2:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.8:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.8.1:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.6.2:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.7:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:.net_framework:4.7.1:*:*:*:*:*:*:*

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