A pair of critical vulnerabilities in Microsoft QUIC were disclosed in Microsoft security updates published October 13, 2026. The National Vulnerability Database (NVD) rates both 9.8 CRITICAL, and both allow an unauthenticated attacker to execute code over a network. Because QUIC ships with Windows and is used by Windows applications and services, any Windows environment that runs the affected component is exposed. Patch these now.
What the vulnerabilities are
Microsoft QUIC is the Windows implementation of the QUIC transport protocol. Two flaws in it were fixed in the October 13, 2026 updates:
- CVE-2026-100219 – a use-after-free in Microsoft QUIC. NVD rates it 9.8 CRITICAL. Per NVD: “Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.” See NVD detail.
- CVE-2026-105016 – a heap-based buffer overflow in Microsoft QUIC. NVD rates it 9.8 CRITICAL. Per NVD: “Heap-based buffer overflow in Microsoft QUIC allows an unauthorized attacker to execute code over a network.” See NVD detail.
Both carry the NVD CVSS base score of 9.8 (CRITICAL) and both require patching.
Why this matters for a business
A 9.8 CRITICAL, network-exploitable remote-code-execution flaw in a core Windows transport component is exactly the kind of gap a threat actor scans for before trying to get in. NVD rates both CVEs CRITICAL because an attacker could exploit them without first authenticating. The exposure applies to any Windows host and server that runs the affected QUIC component.
What to do
- Apply the Microsoft security updates that close CVE-2026-100219 and CVE-2026-105016 to all affected Windows hosts and servers.
- Confirm the updates are installed and the hosts no longer report the vulnerable QUIC version.
- Review network exposure for any Windows host that accepts network traffic to a QUIC listener.
Virtual IT Group can verify your Windows hosts, confirm the patches are in place, and close the remaining gaps. Request a cybersecurity check.
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