Patch tracker / KB5077864
KB5077864: .NET 8.0 installed on Linux Security Update (February 2026)
KB5077864 is a High security update for .NET 8.0 installed on Linux, released 2026-02-10. It closes 1 CVE with a maximum CVSS of 7.5. It is the 23rd largest of the 29 updates Microsoft shipped that month, by CVEs closed.
Update summary
Fixes 1 CVE. Most severe CVSS 7.5 (High). EPSS exploit probability up to 1.0%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for .NET 10.0 installed on Mac OS has shipped since this one: KB5101003 (2026-07-14). 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.
KB5077864 patches CVE-2026-21218, a single High severity flaw (CVSS 7.5) spanning .NET 10.0 on both macOS and Windows plus .NET 8.0 on Linux, so this is a cross-platform runtime fix rather than a Windows-only update. It is not in CISA KEV and carries only a 1% EPSS, meaning no known exploitation to date. The unusual part is the breadth: any Linux, Mac, or Windows host running these .NET versions is in scope, including containers and build agents that are easy to overlook.
Do this: Inventory all .NET 10.0 and .NET 8.0 installations across your Windows, macOS, and Linux hosts, then apply KB5077864 to each affected runtime.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5077864
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5077864
- Released
- 2026-02-10
- Last changed
- 2026-02-10
- 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 KB5077864 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-2026-21218 | High | 7.5 | 1.0% | No |
Scope and sources
- Affected products
- Also released in February 2026
KB5075897
29 CVEs · High · exploitedKB5075899
29 CVEs · High · exploitedKB5075904
24 CVEs · High · exploitedKB5075906
27 CVEs · High · exploitedKB5075912
24 CVEs · High · exploitedKB5075941
26 CVEs · High · exploitedKB5075942
29 CVEs · High · exploitedKB5075943
27 CVEs · High · 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.