Patch tracker / KB5066133
KB5066133: .NET 8.0 installed on Linux Security Update (October 2025)
KB5066133 is a Medium security update for .NET 8.0 installed on Linux, released 2025-10-14. It closes 1 CVE with a maximum CVSS of 4.8. The most likely of them to be attacked is CVE-2025-55248, which FIRST.org rates at 66% probability of exploitation in the next 30 days.
Update summary
Fixes 1 CVE. Most severe CVSS 4.8 (Medium). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for .NET 8.0 installed on Linux has shipped since this one: KB5077862 (2026-02-10). 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.
KB5066133 patches CVE-2025-55248, a single Medium severity flaw (CVSS 4.8) in .NET 8.0 on Linux and macOS plus .NET 9.0 on Linux. This is a cross-platform .NET runtime fix, so the exposure sits on your Linux and Mac hosts running .NET workloads rather than Windows servers. The EPSS is only 1 percent and it is not in CISA KEV, so there is no active exploitation pressure here.
Do this: Update the .NET 8.0 and 9.0 runtimes on your Linux and macOS hosts during your next scheduled patch window.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5066133
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5066133
- Released
- 2025-10-14
- Last changed
- 2025-10-14
- 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 KB5066133 is installed
Elevated PowerShell. No output means it is not installed.
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-2025-55248 | Medium | 4.8 | 66% | No |
Scope and sources
- Affected products
- Also released in October 2025
KB5070879
1 CVE · Critical · exploitedKB5070881
1 CVE · Critical · exploitedKB5070882
1 CVE · Critical · exploitedKB5070883
1 CVE · Critical · exploitedKB5070884
1 CVE · Critical · exploitedKB5070886
1 CVE · Critical · exploitedKB5070887
1 CVE · Critical · exploitedKB5070892
1 CVE · 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.