Patch tracker / KB5077863
KB5077863: .NET 8.0 installed on Linux Security Update (February 2026)
KB5077863 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.
KB5077863 patches a single vulnerability, CVE-2026-21218, spanning .NET 10.0 on both Mac OS and Windows plus .NET 8.0 on Linux, so a mixed shop can be exposed across all three platforms from one flaw. It rates High severity at CVSS 7.5 but the exploitation likelihood is low, with EPSS at 1% and no CISA KEV or ransomware association. The cross-platform reach matters more than the score here, since one runtime bug touches developer workstations and Linux servers alike.
Do this: Inventory every host running .NET 10.0 or .NET 8.0 across Mac, Windows, and Linux, then apply KB5077863 starting with internet-facing .NET 8.0 Linux servers.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5077863
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5077863
- 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 KB5077863 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.