Act nowDisclosed

Advisory · CVE-2026-105016

Heap overflow in Microsoft QUIC also reaches .NET and Visual Studio

Microsoft QUIC has a heap-based buffer overflow an unauthenticated attacker can trigger over the network; the affected list spans Windows, .NET 8 through 11, and Visual Studio. Microsoft rates it CVSS 3.1 9.8.

Advisory published October 13, 2026Independent summary
Vendor
Microsoft
Product
Microsoft QUIC
Identifier / CWE
CVE-2026-105016
CWE-122
Action timing
Immediate
ELI5

Explain it like I’m five

The same QUIC flaw lives in the operating system and in the developer stack, so the vulnerable code travels with applications, not just servers.

SIMPLIFIED_ATTACK_PATH03 STEPS
  1. 01Reach the component

    An unauthenticated attacker sends crafted network traffic to a Windows system running Microsoft QUIC.

  2. 02Memory flaw triggers

    The component mishandles the input and corrupts or reuses memory outside its intended bounds.

  3. 03Code runs

    The attacker gains code execution in the component's context on the target system.

What happened

Microsoft disclosed CVE-2026-105016 in its October 2026 update guide: a heap-based buffer overflow (CWE-122) in Microsoft QUIC. Microsoft’s affected data includes .NET 8.0, 9.0, 10.0, and 11.0 lines, Visual Studio 2022 and 2026, and recent Windows releases.

Microsoft lists the affected Windows releases 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 Microsoft QUIC 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 Microsoft QUIC while remediation is underway, especially for internet-facing instances.
  4. Review application and server logs for QUIC-related crashes in .NET services, and inventories of applications shipping the affected .NET runtimes.
  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

Because this one rides inside .NET, patching Windows Update alone does not close it. Update the runtimes and rebuild or redeploy affected services.