High priorityDisclosed

Advisory · CVE-2026-102869

Type confusion in .NET and Visual Studio can elevate privileges

A type confusion flaw spanning .NET Framework and Visual Studio can let a remote attacker elevate privileges when a victim interacts. Microsoft rates it CVSS 3.1 8.8.

Advisory published October 13, 2026Independent summary
Vendor
Microsoft
Product
.NET Framework
Identifier / CWE
CVE-2026-102869
CWE-843
Action timing
Immediate
ELI5

Explain it like I’m five

The runtime mistakes one kind of object for another, and a crafted project or file can turn that confusion into higher privileges on a developer machine.

SIMPLIFIED_ATTACK_PATH03 STEPS
  1. 01Attacker engages the component

    A remote or authorized attacker sends crafted content or requests to .NET Framework.

  2. 02Weakness triggers

    The component mishandles the input and the flaw takes effect.

  3. 03Impact lands

    The attacker gains the execution, elevation, or access the flaw allows.

What happened

Microsoft disclosed CVE-2026-102869 in its October 2026 update guide: a type confusion weakness (CWE-843) affecting .NET Framework lines and Visual Studio 2022 17.14 and Visual Studio 2026 18.10, with patched thresholds including Visual Studio 17.14.42 and 18.10.4 in Microsoft’s affected data.

Microsoft lists the affected releases and their patched build thresholds in its update guide. Apply the October 2026 security updates for your release rather than relying on a version guess here.

What to do

  1. Inventory every .NET Framework deployment, including test, training, and individually managed instances.
  2. Apply the vendor fix or upgrade exactly as directed in the linked vendor bulletin or advisory.
  3. Restrict network access to .NET Framework while remediation is underway, especially for internet-facing instances.
  4. Review application and server logs for unexpected privilege changes on developer machines and crashes in .NET applications opening untrusted content.
  5. Check for accounts, content, or configuration created outside normal change processes, and rotate exposed credentials where access cannot be ruled out.
  6. Verify the deployed version or patch level after remediation.

Management note

Developer toolchains are high-value targets. Update Visual Studio and the .NET Framework lines together.