CVE-2026-105794

MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL

Published Oct 6, 2026 CVSS 4.0 · 9.1 Critical EPSS 1.0% KEV · Not listed
Description
MsQuic is a cross-platform C implementation of the IETF QUIC protocol exposed to C, C++, C#, and Rust. Prior to 2.4.20, 2.5.11, and 2.6.1, MsQuic clients using the OpenSSL or QuicTLS TLS backend do not properly verify that a server certificate matches the intended target server hostname. An on-path attacker can therefore present a certificate that does not match the intended target hostname and spoof the server in a man-in-the-middle attack. The Schannel backend is not affected. This issue is fixed in versions 2.4.20, 2.5.11, and 2.6.1.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-w5f4-fx9m-m4q7 MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Microsoft
Microsoft msquic
Vendors & Products Microsoft
Microsoft msquic
Type Values Removed Values Added
Description MsQuic is a cross-platform C implementation of the IETF QUIC protocol exposed to C, C++, C#, and Rust. Prior to 2.4.20, 2.5.11, and 2.6.1, MsQuic clients using the OpenSSL or QuicTLS TLS backend do not properly verify that a server certificate matches the intended target server hostname. An on-path attacker can therefore present a certificate that does not match the intended target hostname and spoof the server in a man-in-the-middle attack. The Schannel backend is not affected. This issue is fixed in versions 2.4.20, 2.5.11, and 2.6.1.
Title MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL
Weaknesses CWE-295
References
Metrics cvssV4_0

{'score': 9.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 6, 2026, 5:40 PM
Reserved
Oct 5, 2026, 8:37 PM
Status
Awaiting Analysis
Published
Oct 6, 2026, 3:17 PM
Modified
Oct 6, 2026, 6:16 PM