Patch tracker / KB5099538
KB5099538: Windows Server 2019 Security Update (July 2026)
KB5099538 is a Critical security update for Windows Server 2019, released 2026-07-14. It closes 312 CVEs with a maximum CVSS of 9.9. At least one of them is actively exploited (CISA KEV), so this is a deploy-first update. The most likely of them to be attacked is CVE-2026-42982, which FIRST.org rates at 64% probability of exploitation in the next 30 days.
Update summary
Fixes 312 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.9 (Critical). EPSS exploit probability up to 64%. Among the top 25% of tracked Microsoft updates by EPSS exploit probability.
A newer security update for Windows 10 Version 1809 for 32-bit Systems has shipped since this one: KB5094041 (2026-08-11). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.
Microsoft documents 1 known issue with this update.
- We are currently not aware of any issues with this update.
KB5099538 is an unusually large rollup for Windows 10 1809 and Windows Server 2019, fixing 311 CVEs in a single release with a top Severity of Critical at CVSS 9.9. One of these vulnerabilities is already on the CISA Known Exploited Vulnerabilities list, so at least one flaw is confirmed exploited in the wild even though none are currently tied to ransomware. The peak EPSS of 11 percent is modest, but the KEV listing plus the 9.9 score is what makes this batch a priority for 1809 and Server 2019 fleets still in support.
Do this: Deploy KB5099538 to all Windows 10 1809 and Windows Server 2019 systems now, prioritizing internet-facing servers because of the KEV-listed CVE.
AI-generated from public data, 2026-07-25. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5099538
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5099538
- Released
- 2026-07-14
- Last changed
- 2026-07-29
- Changes tracked
- 3
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.
Microsoft revised KB5099538 on 2026-07-29: CVEs fixed 311 to 312.
- 2026-07-29 CVEs fixed 311 to 312
Recorded by Senserva on the dates shown, from the MSRC release feed. This is what moved and when, which neither the vendor advisory nor NVD publishes.
Check if KB5099538 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5099538 (checked 2026-08-11). Verify against the article before acting.
We are currently not aware of any issues with this update.
Applies to: Windows 10 Enterprise LTSC 2019
This security update includes fixes and quality improvements that are part of the following update:
June 9, 2026—KB5094123 (OS Build 17763.8874)
The following is a summary of the issues that this update addresses when you install this update. The bold text within the brackets indicates the item or area of the change we are documenting.
[Input] This update changes hotkey unregister and cleanup behavior. In rare cases, some built-in Windows experiences that rely on previous hotkey lifecycle behavior might temporarily stop responding to certain keyboard shortcuts. This issue can typically be resolved by restarting the app affected. If the issue is not resolved, report it through the Feedback Hub.
[Secure Boot]
This update enables dynamic status reporting for Secure Boot states in Windows Security App.
This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates . Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.
[File Explorer (known issue)] Fixed: An issue where the OneDrive shortcut in File Explorer stops working when File Explorer is run with administrative mode.
[Networking] This update ...
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.
Scope and sources
- Affected products
- Also released in July 2026
KB5099444
185 CVEs · Critical · exploitedKB5099445
174 CVEs · Critical · exploitedKB5099535
261 CVEs · Critical · exploitedKB5099536
389 CVEs · Critical · exploitedKB5099539
314 CVEs · Critical · exploitedKB5099540
326 CVEs · Critical · exploitedKB5101649
383 CVEs · Critical · exploitedKB5101650
380 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.