CVE-2026-105794 · GHSA-w5f4-fx9m-m4q7
MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL
- Risk score
- 82/100
- CVSS
- 9.1 v4.0
- Exploit chance (30 days)
- 1.0%
- Published
- 6 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- 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 theref…
- Affected
- Microsoft.Native.Quic.MsQuic.OpenSSL (nuget) < 2.4.20; Microsoft.Native.Quic.MsQuic.OpenSSL (nuget) >= 2.5.0, < 2.5.11; Microsoft.Native.Quic.MsQuic.OpenSSL (nuget) >= 2.6.0, < 2.6.1
- Fix
- Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to 2.4.20 or 2.5.11 or 2.6.1 (whichever matches your release line) or later.
- Exploitation
- No known exploitation
Why it is Red
- CVSS 9.1 critical
- Remotely exploitable without logging in
- On your watchlist: openssl, NuGet
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| Microsoft.Native.Quic.MsQuic.OpenSSL | nuget | < 2.4.20 | 2.4.20 |
| Microsoft.Native.Quic.MsQuic.OpenSSL | nuget | >= 2.5.0, < 2.5.11 | 2.5.11 |
| Microsoft.Native.Quic.MsQuic.OpenSSL | nuget | >= 2.6.0, < 2.6.1 | 2.6.1 |
References
- https://github.com/advisories/GHSA-w5f4-fx9m-m4q7
- https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7
- https://nvd.nist.gov/vuln/detail/CVE-2026-105794
- https://github.com/microsoft/msquic/pull/6274
- https://github.com/microsoft/msquic/pull/6275
- https://github.com/microsoft/msquic/pull/6276
- https://github.com/microsoft/msquic/pull/6277
- https://github.com/microsoft/msquic/commit/0591586443cc73a2d2cfb679527d91a144b4a412
- https://github.com/microsoft/msquic/commit/508e811370df93e2ad848f5c78347d4fe4f65a91
- https://github.com/microsoft/msquic/commit/90fd45498bf9b506b8556fb407088688474d6c81
Original 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.
Last activity 6 Oct 2026. Patch Forecast updates every hour.