CVE-2026-103577

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Insecure Default Variable Initialization in Microsoft QUIC

Publication date: 2026-10-13

Last updated on: 2026-10-13

Assigner: Microsoft Corporation

Description

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

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-10-13

Last Modified

2026-10-13

Generated

2026-10-19

AI Q&A

2026-10-14

EPSS Evaluated

2026-10-18

NVD

CVE-2026-103577

EUVD

EUVD-2026-100390

Affected Vendors & Products

Vendor	Product	Version / Range
Microsoft	Windows	11 version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 24H2 10.0.26100.0
Microsoft	Windows	11 Version 25H2 10.0.26200.0
Microsoft	Windows	11 version 26H1 10.0.28000.0
Microsoft	Windows	11 Version 26H2 10.0.26300.0
Microsoft	Windows	Server 2022 10.0.20348.0
Microsoft	Windows	Server 2025 10.0.26100.0
Microsoft	Windows	Server 2025 (Server Core installation) 10.0.26100.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-453	The product, by default, initializes an internal variable with an insecure or less secure value than is possible.

Attack-Flow Graph

Executive Summary

This vulnerability involves insecure default variable initialization in Microsoft QUIC, which allows an unauthorized attacker to bypass a security feature over a network.

Impact Analysis

An attacker could exploit this to bypass security protections, potentially leading to unauthorized access or data exposure on affected systems running Microsoft QUIC.

Compliance Impact

This vulnerability allows unauthorized attackers to bypass security features, which could lead to unauthorized access or data exposure. Such breaches may violate compliance requirements under GDPR (data protection) and HIPAA (health data security) by failing to maintain adequate security controls.

Mitigation Strategies

Apply the latest security updates from Microsoft to address the insecure default variable initialization in QUIC. Monitor Microsoft's update guide for patches and install them promptly.

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