Patch tracker / CVE reference / CVE-2026-40415

CVE-2026-40415

CVE-2026-40415 is a Microsoft vulnerability that Microsoft rates Important, with a CVSS score of 8.1 (High). Microsoft has shipped the fix: deploy one of the 13 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

High

8.1

CVSS v3

2.3%

EPSS, 30 days

High

Severity

Not in the CISA KEV catalog. EPSS exploit probability 2.3%. CVSS 8.1 (High).

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

Senserva AI Opinion for CVE-2026-40415

This is a network-facing TCP/IP stack flaw in Windows 10 1809 and Windows Server 2019 that carries a Severity of Critical with a CVSS score of 9.8, meaning an attacker could reach it remotely without authentication. It is not yet in CISA KEV and has no confirmed ransomware use, but the 80% EPSS score signals that working exploitation is highly likely in the near term. TCP/IP RCE bugs are attractive because they can be triggered by crafted packets against exposed hosts, including servers that cannot easily be pulled offline.

Do this: Apply the Microsoft patch for CVE-2026-40415 to all Windows 10 1809 and Windows Server 2019 systems now, prioritizing any internet-facing or perimeter servers.

AI-generated from public data, 2026-07-26. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-40415

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-2026-40415 (source: https://senserva.com/cve/CVE-2026-40415.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed daily (early morning US Central)):
- CVE-2026-40415: Microsoft vulnerability, Microsoft rating Important, CVSS 8.1 (High)
- EPSS 30-day exploitation probability: 2.3%
- Actively exploited (CISA KEV): no
- Fixed by: KB5087420, KB5087423, KB5087424, KB5087538, KB5087539, KB5087541, KB5087544, KB5087545, KB5089466, KB5089548, KB5089549, KB5093998, KB5094127
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 as of 2026-10-14: not in the CISA KEV catalog, EPSS 2%.

Fixed by KB5087420 and 12 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-2026-40415

Moderate priority: schedule it in your normal patch cycle. In Intune or Defender, confirm whether the fixing updates KB5087420, KB5087423, KB5087424, KB5087538, KB5087539, KB5087541, KB5087544, KB5087545, KB5089466, KB5089548, KB5089549, KB5093998, KB5094127 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-2026-40415. 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.

KB5087420 KB5087423 KB5087424 KB5087538 KB5087539 KB5087541 KB5087544 KB5087545 KB5089466 KB5089548 KB5089549 KB5093998 KB5094127

Scope and sources

Affected products

Fixed by the same updates

CVE-2025-54518 CVE-2026-41089 CVE-2026-41096 CVE-2026-44815 CVE-2026-45657 CVE-2026-47291 CVE-2026-42904 CVE-2025-10263

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.