Patch tracker / KB5087423
KB5087423: Windows 11 Version 25H2 for x64-based Security Update (June 2026)
Updated July 21, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
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Microsoft security update released 2026-06-09. Fixes 66 CVEs.
All about KB5087423: the download, the Senserva AI read, a PowerShell installed-check, install guidance, the CVEs it fixes, and its change history.
KB5087423 is a Critical security update for Windows 11 Version 25H2 for x64-based , released 2026-06-09. It closes 66 CVEs with a maximum CVSS of 9.8. Get it from the Microsoft Update Catalog below, and see where it sits against the rest of the month on the patch tracker.
No exploitation is confirmed yet, but the EPSS model puts the 30-day exploitation probability for the worst CVE here at 72%, which is high enough to treat this as more urgent than its Critical label alone suggests. Attackers reverse-engineer Patch Tuesday updates within days, so the safe assumption is that exploit code follows the patch.
Most organizations deliver an update like this automatically through Intune update rings, Windows Update for Business, Windows Autopatch, or WSUS; the install section below covers each path. For the bigger picture: how the Microsoft patching tools fit together, this month's Patch Tuesday summary, and every update ranked by real-world risk.
Download KB5087423
Get the official update for KB5087423. The download and file size for each supported product are on the Microsoft Update Catalog page.
Update summary
Senserva AI Opinion for KB5087423
KB5087423 is a large rollup fixing 66 CVEs across Windows Server 2025 Server Core and Windows 11 25H2 on both ARM64 and x64. The top flaw carries a Critical rating at CVSS 9.8 with a 72 percent EPSS, meaning exploitation in the wild is statistically likely even though none of these CVEs are on the CISA KEV list yet. The Server Core scope matters because these are often domain controllers and infrastructure hosts where a wormable network-facing bug is most damaging.
Do this: Prioritize this update on Server Core hosts and 25H2 clients now, patching the CVSS 9.8 exposure first before the 72 percent EPSS translates into active attacks.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5087423
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5087423
Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.
Exploitation and severity
Fixes 66 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 72%.
Among the top 25% of tracked Microsoft updates by EPSS exploit probability.
What to do
High priority: EPSS puts the odds of near-term exploitation high. Senserva flags whether KB5087423 is missing on your devices.
Check if KB5087423 is installed
Copy-paste PowerShell: one machine, or your whole fleet in one pass. No output means the update is not installed.
Get-HotFix covers Windows updates. Office, SharePoint, and Exchange server updates show under installed updates in Programs and Features, or check the Update Catalog history.
Writing about KB5087423? Cite this page
Copy-paste for a blog post, forum answer, or internal doc. The link always carries the current risk data.
CVEs fixed by this update
Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.
| CVE | Severity | CVSS | EPSS | Exploited |
|---|---|---|---|---|
| CVE-2025-54518 | Critical | 9.8 | 72% | No |
| CVE-2026-21530 | Critical | 9.8 | 72% | No |
| CVE-2026-32161 | Critical | 9.8 | 72% | No |
| CVE-2026-32170 | Critical | 9.8 | 72% | No |
| CVE-2026-32209 | Critical | 9.8 | 72% | No |
| CVE-2026-33834 | Critical | 9.8 | 72% | No |
| CVE-2026-33835 | Critical | 9.8 | 72% | No |
| CVE-2026-33837 | Critical | 9.8 | 72% | No |
| CVE-2026-33838 | Critical | 9.8 | 72% | No |
| CVE-2026-33839 | Critical | 9.8 | 72% | No |
| CVE-2026-33840 | Critical | 9.8 | 72% | No |
| CVE-2026-33841 | Critical | 9.8 | 72% | No |
| CVE-2026-34329 | Critical | 9.8 | 72% | No |
| CVE-2026-34330 | Critical | 9.8 | 72% | No |
| CVE-2026-34331 | Critical | 9.8 | 72% | No |
| CVE-2026-34332 | Critical | 9.8 | 72% | No |
| CVE-2026-34333 | Critical | 9.8 | 72% | No |
| CVE-2026-34334 | Critical | 9.8 | 72% | No |
| CVE-2026-34336 | Critical | 9.8 | 72% | No |
| CVE-2026-34337 | Critical | 9.8 | 72% | No |
| CVE-2026-34338 | Critical | 9.8 | 72% | No |
| CVE-2026-34339 | Critical | 9.8 | 72% | No |
| CVE-2026-34340 | Critical | 9.8 | 72% | No |
| CVE-2026-34341 | Critical | 9.8 | 72% | No |
| CVE-2026-34342 | Critical | 9.8 | 72% | No |
| CVE-2026-34343 | Critical | 9.8 | 72% | No |
| CVE-2026-34344 | Critical | 9.8 | 72% | No |
| CVE-2026-34345 | Critical | 9.8 | 72% | No |
| CVE-2026-34347 | Critical | 9.8 | 72% | No |
| CVE-2026-34350 | Critical | 9.8 | 72% | No |
| CVE-2026-34351 | Critical | 9.8 | 72% | No |
| CVE-2026-35415 | Critical | 9.8 | 72% | No |
| CVE-2026-35416 | Critical | 9.8 | 72% | No |
| CVE-2026-35417 | Critical | 9.8 | 72% | No |
| CVE-2026-35418 | Critical | 9.8 | 72% | No |
| CVE-2026-35419 | Critical | 9.8 | 72% | No |
| CVE-2026-35420 | Critical | 9.8 | 72% | No |
| CVE-2026-35421 | Critical | 9.8 | 72% | No |
| CVE-2026-35422 | Critical | 9.8 | 72% | No |
| CVE-2026-35423 | Critical | 9.8 | 72% | No |
| CVE-2026-35424 | Critical | 9.8 | 72% | No |
| CVE-2026-40369 | Critical | 9.8 | 72% | No |
| CVE-2026-40377 | Critical | 9.8 | 72% | No |
| CVE-2026-40380 | Critical | 9.8 | 72% | No |
| CVE-2026-40382 | Critical | 9.8 | 72% | No |
| CVE-2026-40397 | Critical | 9.8 | 72% | No |
| CVE-2026-40398 | Critical | 9.8 | 72% | No |
| CVE-2026-40399 | Critical | 9.8 | 72% | No |
| CVE-2026-40401 | Critical | 9.8 | 72% | No |
| CVE-2026-40403 | Critical | 9.8 | 72% | No |
| CVE-2026-40405 | Critical | 9.8 | 72% | No |
| CVE-2026-40406 | Critical | 9.8 | 72% | No |
| CVE-2026-40407 | Critical | 9.8 | 72% | No |
| CVE-2026-40408 | Critical | 9.8 | 72% | No |
| CVE-2026-40410 | Critical | 9.8 | 72% | No |
| CVE-2026-40413 | Critical | 9.8 | 72% | No |
| CVE-2026-40414 | Critical | 9.8 | 72% | No |
| CVE-2026-40415 | Critical | 9.8 | 72% | No |
| CVE-2026-41088 | Critical | 9.8 | 72% | No |
| CVE-2026-41089 | Critical | 9.8 | 72% | No |
| CVE-2026-41095 | Critical | 9.8 | 72% | No |
| CVE-2026-41096 | Critical | 9.8 | 72% | No |
| CVE-2026-41097 | Critical | 9.8 | 72% | No |
| CVE-2026-42825 | Critical | 9.8 | 72% | No |
| CVE-2026-42896 | Critical | 9.8 | 72% | No |
| CVE-2026-48566 | Critical | 9.8 | 72% | No |
Affected products
Also released in June 2026
The highest-risk updates from the same release:
The full month, summarized: Microsoft Patch Tuesday.
How to install KB5087423
Any of these paths delivers KB5087423; most organizations already have one of the first three running:
- Intune update rings (Windows Update for Business): the update flows on each ring's deferral schedule.
- Windows Autopatch: rings, rollout, and pause or rollback are managed for you; exploited updates can be expedited.
- WSUS / Configuration Manager: approve KB5087423 for your device groups and set a deadline.
- Manual: download from the Update Catalog above and install; fine for a handful of machines, unmanageable at any real scale.
After the rollout, verify rather than assume: update compliance reporting in Intune or Autopatch shows which devices actually installed it, and Siemserva reads Intune, Defender, Autopatch, and Azure Update Manager together to show the devices still missing KB5087423, ranked by exploitation.
Common questions about KB5087423
Is KB5087423 urgent?
KB5087423 is rated Critical with a maximum CVSS of 9.8. No active exploitation is confirmed yet, so schedule it in your prompt patch cycle.
How do I download KB5087423?
From the Microsoft Update Catalog (linked on this page), or let Intune, Windows Update for Business, Windows Autopatch, or WSUS deliver it. The catalog page lists the download for each supported product.
How do I deploy KB5087423 with Intune?
Assign a Windows Update ring (quality update policy) to the device groups and the update flows on the ring's deferral schedule. For urgent updates, Intune expedite policies can bypass the ring deferrals. Verify the rollout with update compliance reporting rather than assuming delivery.
Can I ask my own AI about KB5087423?
Yes. This page includes a free, ready-to-paste AI prompt containing KB5087423's key facts: severity, CVE count, exploitation status, and the download link. Copy it into Claude, ChatGPT, or Copilot for a rollout plan; the data is refreshed three times a day (5 AM, 12:30 PM, and 7 PM US Central).
Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.
