Patch tracker / KB5126655
KB5126655: Windows Server 2022 Security Update (October 2026)
KB5126655 is a Critical security update for Windows Server 2022, released 2026-10-13. It closes 977 CVEs with a maximum CVSS of 9.8. At least one of them is actively exploited (CISA KEV), so this is a deploy-first update. It is the fourth largest of the 75 updates Microsoft shipped that month, by CVEs closed.
Update summary
Fixes 977 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). This update fixes an actively-exploited (CISA KEV) vulnerability.
Microsoft documents 1 known issue with this update.
- Windows Server Update Services (WSUS) does not display error details
Senserva AI Opinion and rich prompt for KB5126655
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5126655
- Released
- 2026-10-13
- Last changed
- 2026-10-13
- Changes tracked
- 1
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 KB5126655 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5126655 (checked 2026-10-13). Verify against the article before acting.
Windows Server Update Services (WSUS) does not display error details
After installing KB5070884 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.
What the press says about this update
Trusted-source coverage of the CVEs this update fixes, pulled live from their own feeds.
Scope and sources
- Affected products
- Also released in October 2026
KB5099444
186 CVEs · Critical · exploitedKB5099445
175 CVEs · Critical · exploitedKB5099535
262 CVEs · Critical · exploitedKB5099536
390 CVEs · Critical · exploitedKB5099538
313 CVEs · Critical · exploitedKB5099539
315 CVEs · Critical · exploitedKB5099540
327 CVEs · Critical · exploitedKB5101649
384 CVEs · Critical · exploitedThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.