Patch tracker / KB5087423

KB5087423: Windows 11 Version 25H2 for x64-based Security Update (June 2026)

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. The most likely of them to be attacked is CVE-2026-48566, which FIRST.org rates at 80% probability of exploitation in the next 30 days.

Update summary

Critical
2026-06-09
Released
66
CVEs fixed
9.8
Max CVSS
Critical
Severity
Deploy this cycle
Fixes 66 CVEs for Windows 11 Version 25H2 for x64-based . No confirmed in-the-wild exploitation in this set today.

Fixes 66 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 80%. Among the top 10% of tracked Microsoft updates by EPSS exploit probability.

Senserva found thisread these before you deploy broadly

Microsoft documents 1 known issue with this update.

  • Windows Server Update Services (WSUS) does not display error details

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5087423Microsoft support article
Senserva AI Opinion for KB5087423

KB5087423 is a large rollup fixing 66 CVEs for Windows Server 2025 Server Core and Windows 11 25H2 on ARM64 and x64. The top flaw rates Critical at CVSS 9.8 with an 80 percent EPSS score, meaning exploitation is likely even though nothing here is currently in CISA KEV or tied to ransomware. Exposed systems include Server Core hosts, which are often domain controllers or infrastructure roles where a remote unauthenticated bug would be especially damaging.

Do this: Prioritize deploying KB5087423 to internet-facing and Server Core hosts first, given the CVSS 9.8 and 80 percent EPSS on the top CVE.

AI-generated from public data, 2026-07-26. 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

Released
2026-06-09
Last changed
2026-07-24
Changes tracked
2

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.

Check if KB5087423 is installed

Elevated PowerShell. No output means it is not installed.

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5087423 (checked 2026-08-05). Verify against the article before acting.

Windows Server Update Services (WSUS) does not display error details

After installing KB5070893 or later updates, Windows Server Update Services (WSUS) does not display synchronization error details within its error reporting. This functionality is temporarily removed to address the Remote Code Execution Vulnerability, CVE-2025-59287 .

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.

CVESeverityCVSSEPSSExploited
CVE-2025-54518Critical9.880%No
CVE-2026-21530Critical9.880%No
CVE-2026-32161Critical9.880%No
CVE-2026-32170Critical9.880%No
CVE-2026-32209Critical9.880%No
CVE-2026-33834Critical9.880%No
CVE-2026-33835Critical9.880%No
CVE-2026-33837Critical9.880%No
CVE-2026-33838Critical9.880%No
CVE-2026-33839Critical9.880%No
CVE-2026-33840Critical9.880%No
CVE-2026-33841Critical9.880%No
CVE-2026-34329Critical9.880%No
CVE-2026-34330Critical9.880%No
CVE-2026-34331Critical9.880%No
CVE-2026-34332Critical9.880%No
CVE-2026-34333Critical9.880%No
CVE-2026-34334Critical9.880%No
CVE-2026-34336Critical9.880%No
CVE-2026-34337Critical9.880%No
CVE-2026-34338Critical9.880%No
CVE-2026-34339Critical9.880%No
CVE-2026-34340Critical9.880%No
CVE-2026-34341Critical9.880%No
CVE-2026-34342Critical9.880%No
CVE-2026-34343Critical9.880%No
CVE-2026-34344Critical9.880%No
CVE-2026-34345Critical9.880%No
CVE-2026-34347Critical9.880%No
CVE-2026-34350Critical9.880%No
CVE-2026-34351Critical9.880%No
CVE-2026-35415Critical9.880%No
CVE-2026-35416Critical9.880%No
CVE-2026-35417Critical9.880%No
CVE-2026-35418Critical9.880%No
CVE-2026-35419Critical9.880%No
CVE-2026-35420Critical9.880%No
CVE-2026-35421Critical9.880%No
CVE-2026-35422Critical9.880%No
CVE-2026-35423Critical9.880%No
CVE-2026-35424Critical9.880%No
CVE-2026-40369Critical9.880%No
CVE-2026-40377Critical9.880%No
CVE-2026-40380Critical9.880%No
CVE-2026-40382Critical9.880%No
CVE-2026-40397Critical9.880%No
CVE-2026-40398Critical9.880%No
CVE-2026-40399Critical9.880%No
CVE-2026-40401Critical9.880%No
CVE-2026-40403Critical9.880%No
CVE-2026-40405Critical9.880%No
CVE-2026-40406Critical9.880%No
CVE-2026-40407Critical9.880%No
CVE-2026-40408Critical9.880%No
CVE-2026-40410Critical9.880%No
CVE-2026-40413Critical9.880%No
CVE-2026-40414Critical9.880%No
CVE-2026-40415Critical9.880%No
CVE-2026-41088Critical9.880%No
CVE-2026-41089Critical9.880%No
CVE-2026-41095Critical9.880%No
CVE-2026-41096Critical9.880%No
CVE-2026-41097Critical9.880%No
CVE-2026-42825Critical9.880%No
CVE-2026-42896Critical9.880%No
CVE-2026-48566Critical9.880%No

Scope and sources

Affected products
Also released in June 2026

KB5094139

8 CVEs · High · exploited

KB5094140

8 CVEs · High · exploited

KB5094142

8 CVEs · High · exploited

KB5094144

8 CVEs · High · exploited

KB5087539

66 CVEs · Critical

KB5089466

61 CVEs · Critical

KB5089549

61 CVEs · Critical

KB5093998

158 CVEs · Critical

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5087423 page (Microsoft Support)Microsoft Update CatalogMicrosoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
Provided as is, without warranty; verify against the vendor advisory before acting. Data notice and terms.