Patch tracker / KB5122105
KB5122105: .NET 9.0 runtime installed Security Update (August 2026)
KB5122105 is a High security update for .NET 9.0 runtime installed, released 2026-08-11. It closes 10 CVEs with a maximum CVSS of 7.8. It is the 22nd largest of the 76 updates Microsoft shipped that month, by CVEs closed.
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Update summary
Fixes 10 CVEs. Most severe CVSS 7.8 (High). EPSS exploit probability up to 1.2%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
A newer security update for .NET 9.0 runtime installed on Windows has shipped since this one: KB5130035 (2026-10-13). 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.
KB5122105 is the .NET 9.0 runtime update released 2026-08-11, covering Windows, Linux, and Mac OS and fixing 9 CVEs, with a highest Severity of High (CVSS 7.8). It is unusual because one servicing release spans all three operating systems, so mixed-platform shops have to patch more than one build pipeline or image. No fixed CVE is in CISA KEV or ransomware-linked, and the highest EPSS is 1%, so this is a prompt routine patch rather than an emergency.
Do this: Inventory hosts, containers, and build agents running the .NET 9.0 runtime on Windows, Linux, and Mac OS, then roll KB5122105 to them through your normal patch cycle, starting with internet-facing apps.
AI-generated from public data, 2026-11-10. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5122105
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5122105
- Released
- 2026-08-11
- Last changed
- 2026-11-11
- Changes tracked
- 5
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 KB5122105 is installed
This update is for .NET 9.0 runtime installed on Windows, not a Windows component, so Get-HotFix does not list it. Compare the installed version of the product with the build Microsoft lists for 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.
| CVE | Severity | CVSS | EPSS | Exploited |
|---|---|---|---|---|
| CVE-2026-62871 | High | 7.8 | <1% | No |
| CVE-2026-62886 | High | 7.8 | <1% | No |
| CVE-2026-62909 | High | 7.8 | <1% | No |
| CVE-2026-70354 | High | 7.8 | <1% | No |
| CVE-2026-62898 | High | 7.5 | 1.0% | No |
| CVE-2026-62901 | High | 7.5 | 1.2% | No |
| CVE-2026-62897 | High | 7.0 | <1% | No |
| CVE-2026-62902 | Medium | 6.5 | <1% | No |
| CVE-2026-62899 | Medium | 5.9 | <1% | No |
| CVE-2026-62900 | Medium | 5.9 | <1% | No |
Scope and sources
- Affected products
- Also released in August 2026
KB5120228
216 CVEs · Critical · exploitedKB5120229
195 CVEs · Critical · exploitedKB5120233
216 CVEs · Critical · exploitedKB5120238
183 CVEs · Critical · exploitedKB5120240
170 CVEs · Critical · exploitedKB5120242
195 CVEs · Critical · exploitedKB5120385
144 CVEs · Critical · exploitedKB5120386
139 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.