CVE-2026-105794 — MsQuic: Improper Certificate Validation in...

CRITICAL

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

Published October 6, 2026Updated October 6, 2026Source: osv

Summary

# Summary Improper TLS hostname verification allows a man-in-the-middle (MITM) attack on MsQuic. # Details Only MsQuic with the OpenSSL and QuicTLS TLS backends is affected (the Schannel backend is not affected). ## Patches 2.6.1, 2.5.11, and 2.4.20 # Impact An on-path attacker could spoof a server identity by using a certificate that doesn't match the intended target server hostname.

Advisory Timeline

First published October 6, 2026 (6 days ago).
Last revised October 6, 2026 — 0 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

NuGet

Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.4.20 or later

dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.4.20

NuGet

Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.6.1 or later

dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.6.1

NuGet

Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.5.11 or later

dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.5.11

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (3)

Affects 1 ecosystem: nuget (1).

Package	Ecosystem	Affected	Fixed In
Microsoft.Native.Quic.MsQuic.OpenSSL	nuget	1.8.0	2.4.20
Microsoft.Native.Quic.MsQuic.OpenSSL	nuget	All versions	2.6.1
Microsoft.Native.Quic.MsQuic.OpenSSL	nuget	All versions	2.5.11

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-295
Improper Certificate ValidationMITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 8.6 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

—

Confidentiality

—

Integrity

—

Availability

—

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

References

Frequently Asked Questions

What is CVE-2026-105794?: MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 8.6/10).
How do I check if my project is affected by CVE-2026-105794?: CVE-2026-105794 affects Microsoft.Native.Quic.MsQuic.OpenSSL. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-105794 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

8.6

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-w5f4-fx9m-m4q7

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