CVE-2026-103577: Microsoft QUIC Security Feature Bypass Vulnerability

Overview

Severity
High (CVSS 7.5)
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H/E:U/RL:O/RC:C
Category
Security Feature Bypass
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-Oct
Released
2026-10-13

Description

Insecure default variable initialization in Microsoft QUIC allows an unauthorized attacker to bypass a security feature over a network.

FAQ

According to the CVSS metric, the attack vector is network (AV:N), privilege required is none (PR:N), and user interaction is none (UI:N). What is the target used in the context of the security feature bypass? An attacker without existing privileges can remotely bypass authentication and obtain a successful login without additional user interaction. According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability? Successful exploitation of this vulnerability requires an attacker to have a deep understanding of the system. Successful exploitation is not guaranteed and depends on a combination of factors that might include the environment, system configuration, and the presence of additional security measures.

Affected Products (14)

Windows

  • Windows 11 Version 26H2 for ARM64-based Systems
  • Windows 11 Version 26H2 for x64-based Systems
  • Windows Server 2022 (Server Core installation)
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows Server 2025
  • Windows Server 2022
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows Server 2025 (Server Core installation)
  • Windows 11 Version 26H1 for ARM64-based Systems
  • Windows 11 version 26H1 for x64-based Systems

Security Updates (5)

Acknowledgments

<a href="https://novice-22.com/">novice-22</a>, PuH4ck3rX, <a href="https://x.com/shibi_kishore">Shibi Kishore N</a>, Anonymous, <a href="https://x.com/soaj1664ashar">Dr.-Ing Ashar Javed</a>, Liang Zhu, Lucas Futures, <a href="https://instagram.com/aeqkin">Samuel</a> with <a href="https://github.com/samuelgirmametaferia">Independent</a>

Revision History

  • 2026-10-13: Information published.