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Microsoft QUIC implementation as integrated within multiple modern versions of .NET on Windows contains a critical vulnerability related to how incoming network traffic is processed. Specifically, the flaw resides in the handling of HTTP/3 protocol stacks where specially crafted IPv6 QUIC packets can reach the target path without requiring any prior authentication or user interaction. When these malformed data packets are parsed, they trigger a severe memory corruption vulnerability known as a heap-based buffer overflow. This flaw allows an unauthenticated remote attacker to execute arbitrary machine instructions under the security context of the application process. Because the affected network path processes packets directly at the transport layer before session establishment, systems running exposed services are at immediate risk of complete remote compromise without logging any successful interactive login sessions.
DailyCVE Form:
Platform: Windows
Version: .NET 8.0-11 RC2
Vulnerability : Heap-based Buffer Overflow
Severity: Critical
date: 2026-10-13
Prediction: 2026-10-13
What Undercode Say: Analytics
The vulnerability stems from insufficient bounds checking when handling variable-length packet parameters in the Microsoft QUIC protocol stack implementation. Attackers target the IPv6 UDP datagram endpoints handling HTTP/3 connections to corrupt adjacent memory heaps, manipulating function pointers or execution flows.
Bash Commands and Codes
Check installed .NET versions and runtime environment details dotnet --info Update Microsoft.Native.Quic.MsQuic.Schannel package reference via CLI dotnet add package Microsoft.Native.Quic.MsQuic.Schannel --version 2.5.11-ci.159417053
Exploit: (Educational Purposes!)
An unauthenticated remote attacker transmits a heavily manipulated, malformed IPv6 QUIC packet directly targeting the HTTP/3 listener port of a vulnerable .NET application. The packet bypasses standard handshake authentication routines due to improper length validations during initial packet disassembly. As the input buffer overflows the heap allocation boundaries, critical execution structures are overwritten, enabling arbitrary command execution or shell deployment by the remote adversary.
Protection: from this CVE
Administrators and developers must immediately update their environments by installing the latest official servicing updates for their supported .NET releases through Visual Studio or the system package manager. For projects referencing the package directly, upgrade the Microsoft.Native.Quic.MsQuic.Schannel reference to version 2.5.11-ci.159417053 or later. Following package updates, all running services and self-contained application deployments must be fully restarted, recompiled, and redeployed to ensure the vulnerable runtime code is purged from memory.
Impact:
Successful exploitation of this vulnerability results in full remote code execution capabilities on the target Windows system hosting the vulnerable .NET application. An attacker can compromise confidentiality, integrity, and availability by executing arbitrary malicious payloads with the privileges of the running application service worker.
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Sources:
Reported By: github.com
Extra Source Hub:
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