CVE-2026-105016 – Microsoft QUIC Remote Code Execution Vulnerability

Microsoft has identified a critical Remote Code Execution (RCE) vulnerability in Microsoft QUIC that could allow an unauthenticated attacker to execute malicious code on affected systems over a network. The vulnerability, tracked as CVE-2026-105016, is caused by a heap-based buffer overflow and carries a CVSS score of 9.8, making it one of the most severe categories of security vulnerabilities. An attacker could exploit this weakness by sending a specially crafted network packet to an affected service, potentially gaining control of the targeted system without requiring authentication or user interaction. The vulnerability affects multiple Microsoft products, including Windows 11, Windows Server, .NET, and Visual Studio.

CVSS SCORE: 9.8

SEVERITY: Critical

Threat

This vulnerability presents a significant security threat because it allows attackers to execute malicious code remotely without requiring valid credentials or user interaction.

The attack can be launched over a network, and its low attack complexity makes exploitation particularly concerning.

Successful exploitation could allow attackers to compromise vulnerable systems, access sensitive information, modify critical data, or disrupt essential services.

The vulnerability carries a high impact rating across confidentiality, integrity, and availability, meaning a successful attack could affect all three fundamental aspects of system security.

Exploits

Microsoft has classified this vulnerability as “Exploitation Less Likely.”

At the time of publication, the vulnerability was not publicly disclosed and had not been reported as exploited in the wild.

The exploit code maturity is classified as “Unproven,” indicating that working exploit code has not been established.

There is no confirmed evidence of publicly available proof-of-concept (PoC) exploit code or active zero-day exploitation.

However, the vulnerability’s network-based attack vector, low attack complexity, and lack of authentication requirements make it a serious security concern.

Technical Summary

CVE-2026-105016 is a critical heap-based buffer overflow vulnerability (CWE-122) affecting Microsoft QUIC.

QUIC is a network transport protocol designed to provide efficient and secure communication between systems.

The vulnerability occurs when an affected Microsoft QUIC implementation processes specially crafted network packets, potentially triggering a heap-based buffer overflow.

A heap-based buffer overflow occurs when a program writes more data into a memory buffer than it can safely accommodate. This can corrupt adjacent memory and potentially allow attackers to manipulate program execution.

An unauthenticated attacker could exploit this vulnerability by sending a specially crafted packet to an affected service over the network.

If exploitation succeeds, the attacker could execute arbitrary code on the targeted system.

The vulnerability has several concerning technical characteristics:

• Attack Vector: Network — Exploitation can occur remotely.
• Attack Complexity: Low — No complex attack conditions are required.
• Privileges Required: None — Attackers do not need valid credentials.
• User Interaction: None — No action from a user is necessary.
• Confidentiality Impact: High — Sensitive information could be exposed.
• Integrity Impact: High — Attackers could modify or compromise system data.
• Availability Impact: High — Systems and services could experience disruption.

These characteristics make the vulnerability particularly dangerous for organizations operating affected network-accessible systems.

Exploitability

The vulnerability affects several Microsoft products, including:

• Windows 11: Versions 23H2, 24H2, 25H2, and 26H1 on x64 and ARM64 systems.
• Windows Server: Windows Server 2022 and Windows Server 2025, including Server Core installations.
• Microsoft .NET: Versions 8.0, 9.0, 10.0, and 11.0 installed on Windows.
• Microsoft Visual Studio: Visual Studio 2022 version 17.14 and Visual Studio 2026 version 18.10.

An attacker could exploit the vulnerability remotely by sending a specially crafted network packet to an affected service.

No authentication or user interaction is required, making vulnerable network-accessible systems potential targets.

Business Impact

CVE-2026-105016 poses a significant risk to organizations because successful exploitation could allow attackers to execute malicious code on affected Windows systems and servers.

The vulnerability’s critical severity and ability to be exploited remotely make it particularly concerning for enterprise environments.

Potential business consequences include:

• Unauthorized System Access: Attackers could execute malicious code on compromised systems, potentially gaining control over affected services.
• Sensitive Data Exposure: Successful exploitation could expose confidential business information, customer records, or other sensitive data.
• Operational Disruption: Compromised servers and applications could experience outages, affecting business operations and service availability.
• Data Manipulation: Attackers could potentially modify or corrupt important business information.
• Financial and Reputational Damage: Security incidents involving compromised systems could result in recovery costs, operational losses, and reduced customer confidence.

Organizations running affected Windows Server environments face particular concerns because these systems may support critical business applications and infrastructure.

“When attackers can execute code remotely without credentials, a single vulnerable server can become a serious business security risk.”

Workaround

Microsoft has not identified any official workarounds or mitigations for this vulnerability.

Organizations should prioritize installing the applicable Microsoft security updates.

Where immediate patching is not possible, organizations may consider temporarily restricting network access to affected services and limiting exposure of vulnerable systems.

These precautions may reduce exposure but are not confirmed fixes for the vulnerability.

Urgency

Immediate patching is strongly recommended due to the Critical severity rating and CVSS score of 9.8.

Although Microsoft considers exploitation less likely and has not reported active exploitation, the vulnerability presents a serious potential security risk.

Its combination of network-based exploitation, low attack complexity, and zero authentication requirements makes it particularly concerning.

Organizations should prioritize security updates for affected Windows servers, network-accessible systems, and business-critical infrastructure.

Relevant security updates include:

• Windows 11 23H2: KB5126653
• Windows 11 24H2 and 25H2: KB5127648
• Windows 11 26H1: KB5127646
• Windows Server 2022: KB5126655
• Windows Server 2025: KB5126646

Affected .NET and Visual Studio installations should also receive their applicable security updates.

A system restart is required after installing the applicable updates.

Because no official workaround is available, applying the security updates is the recommended method of addressing this vulnerability.