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Microsoft Security Response CenterCVE-2026-62871

.NET Elevation of Privilege Vulnerability

Out-of-bounds write in .NET allows an unauthorized attacker to execute code locally.

Read the vendor bulletin Get alerts for NET 8.0 installed on Windows
7.8CVSS out of 10High severity
Scope

What the vendor says is affected

  • .NET 8.0 installed on Windows
  • .NET 9.0 installed on Windows
  • Microsoft Visual Studio 2026 version 18.8
  • Microsoft Visual Studio 2022 version 17.14

Versions the vendor lists as fixed

  • 8.0.30
  • 9.0.19
  • 18.8.3
  • 17.14.38
Next step

What the vendor recommends

Install KB5122104. Install KB5122105.

Review the complete instructions on the vendor's site
Update history

What changed in later vendor updates

SecurityAlert records field-level changes from the point we begin following a bulletin. Earlier vendor changes may not have a field-by-field record.

    • The vendor changed its remediation guidance.
Timeline

When this advisory changed

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Updated by Microsoft Security Response Center

    The vendor changed the advisory after it was first published.

  3. Added to SecurityAlert

    We collected the advisory from the official source.

  4. Confirmed at the source

    Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-62871View CVSS, KEV, EPSS, and threat context
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