Patch tracker / CVE reference / CVE-2026-23666

CVE-2026-23666

CVE-2026-23666 is a high severity Microsoft vulnerability with a CVSS score of 7.5. Microsoft has shipped the fix: deploy one of the 18 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

High

7.5

CVSS v3

2.1%

EPSS, 30 days

High

Severity

Not in the CISA KEV catalog. EPSS exploit probability 2.1%. CVSS 7.5 (High).

This CVE is among the lower half of tracked Microsoft CVEs by EPSS exploit probability.

Senserva AI Opinion for CVE-2026-23666

CVE-2026-23666 is a High severity (CVSS 7.5) Denial of Service flaw in .NET Framework 4.8 running on the older Windows 10 Version 1607 (32-bit and x64) and Windows Server 2012. Exposure is limited to these legacy platforms, and while it is not in CISA KEV and has only a 2 percent EPSS score, a successful attack can crash .NET-hosted services rather than expose data. If you still run apps on these end-of-support-era builds, an unauthenticated availability hit is the concern.

Do this: Deploy the .NET Framework 4.8 update for Windows 10 1607 and Windows Server 2012, prioritizing servers hosting production .NET workloads.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-23666

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin assessing a vulnerability. Facts for CVE-2026-23666 (source: https://senserva.com/cve/CVE-2026-23666.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2026-23666: High severity Microsoft vulnerability, CVSS 7.5
- EPSS 30-day exploitation probability: 2.1%
- Actively exploited (CISA KEV): no
- Fixed by: KB5082398, KB5082400, KB5082402, KB5082403, KB5082404, KB5082406, KB5082411, KB5082413, KB5082414, KB5082417, KB5082418, KB5082419, KB5082420, KB5082421, KB5082424, KB5082425, KB5082426, KB5082427
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Schedule normally

No exploitation observed: not in the CISA KEV catalog, EPSS 2%.

Fixed by KB5082398 and 17 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Deploy with your normal update cycle. This page refreshes daily; the verdict changes the day the data does.

Official patch(es) for CVE-2026-23666

Moderate priority: schedule it in your normal patch cycle. In Intune or Defender, confirm whether the fixing updates KB5082398, KB5082400, KB5082402, KB5082403, KB5082404, KB5082406, KB5082411, KB5082413, KB5082414, KB5082417, KB5082418, KB5082419, KB5082420, KB5082421, KB5082424, KB5082425, KB5082426, KB5082427 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Apply the Microsoft security updates below to fix CVE-2026-23666. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.

KB5082398 KB5082400 KB5082402 KB5082403 KB5082404 KB5082406 KB5082411 KB5082413 KB5082414 KB5082417 KB5082418 KB5082419 KB5082420 KB5082421 KB5082424 KB5082425 KB5082426 KB5082427

Scope and sources

Affected products

Fixed by the same updates

CVE-2026-33116 CVE-2026-32226

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC FIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.