Patch tracker / KB5073379
KB5073379: Windows 10 Version 1809 for 32-bit Sys Security Update (January 2026)
KB5073379 is a Critical security update for Windows 10 Version 1809 for 32-bit Sys, released 2026-01-13. It closes 86 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. The most likely of them to be attacked is CVE-2026-20962, which FIRST.org rates at 75% probability of exploitation in the next 30 days.
Update summary
Fixes 86 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 75%. Among the top 10% of tracked Microsoft updates by EPSS exploit probability.
A newer security update for Windows 11 Version 25H2 for x64-based Systems has shipped since this one: KB5087423 (2026-06-09). 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 3 known issues with this update.
- Windows Server Update Services (WSUS) does not display error details
- Connection and authentication failures in Azure Virtual Desktop and Windows 365
- Apps might become unresponsive when saving files to cloud-based storage
KB5073379 is a January 2026 rollup fixing 86 CVEs across Windows 11 25H2 (x64 and ARM64) and the older Windows 10 1809, topped by a Critical flaw at CVSS 9.8 with a 74% EPSS score. One of these CVEs is already on the CISA KEV list, meaning it is being exploited in the wild, though none are tied to ransomware campaigns yet. The mix of a confirmed-exploited bug and a near-worst-case remote flaw makes this batch a priority rather than routine patching.
Do this: Deploy KB5073379 to all Windows 11 25H2 and Windows 10 1809 systems now, prioritizing internet-facing hosts because of the KEV-listed and CVSS 9.8 CVEs.
AI-generated from public data, 2026-07-25. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5073379
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5073379
- Released
- 2026-01-13
- Last changed
- 2026-08-04
- 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.
Check if KB5073379 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5073379 (checked 2026-08-04). Verify against the article before acting.
Windows Server Update Services (WSUS) does not display error details
After installing KB5070881 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 .
Connection and authentication failures in Azure Virtual Desktop and Windows 365
Symptoms
After installing the January 2026 security update ( KB5073379 ), released on January 13, 2026, credential prompt failures occurred during Remote Desktop connections using the Windows App on Windows client devices, impacting Azure Virtual Desktop and Windows 365. The issue affects Windows App on specific Windows builds, causing sign-in failures.
Workaround
This issue is addressed in KB5077793 .
Apps might become unresponsive when saving files to cloud-based storage
Symptom
After installing this update, some applications may become unresponsive or encounter unexpected errors when opening files from or saving files to cloud-based storage, such as OneDrive or Dropbox. In certain Outlook configurations that store PST files on OneDrive, Outlook may hang and fail to reopen unless the process is terminated or the system is restarted. Users may also see missing sent Items or previously downloaded emails being re‑downloaded.
Workaround
If you are experiencing this ...
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 January 2026
KB5002822
6 CVEs · Critical · exploitedKB5002825
7 CVEs · Critical · exploitedKB5002828
7 CVEs · Critical · exploitedKB5073450
80 CVEs · Critical · exploitedKB5073455
80 CVEs · Critical · exploitedKB5073457
78 CVEs · Critical · exploitedKB5073722
54 CVEs · Critical · exploitedKB5073723
73 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.