CVE-2026-105794 MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL
MsQuic clients using OpenSSL or QuicTLS fail to validate server hostnames, allowing on-path attackers to spoof servers via man-in-the-middle attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-105794?
CVE-2026-105794 is a critical vulnerability in microsoft msquic, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-295
Which versions are affected by CVE-2026-105794?
6 open source packages ship an affected version, including Microsoft.Native.Quic.MsQuic.OpenSSL.
| Package | Affected | Fixed in |
|---|---|---|
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | All versions | 2.4.20 |
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | All versions | 2.4.20 |
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | From 2.5.0 | 2.5.11 |
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | From 2.5.0 | 2.5.11 |
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | From 2.6.0 | 2.6.1 |
Microsoft.Native.Quic.MsQuic.OpenSSL NuGet | From 2.6.0 | 2.6.1 |
How do I fix CVE-2026-105794?
Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to a fixed version for your release line: 2.4.20, 2.5.11 or 2.6.1.
Is CVE-2026-105794 being exploited?
There is no known exploitation of CVE-2026-105794 in the wild and no public exploit code.
Sources
Also known as GHSA-w5f4-fx9m-m4q7.