CVE-2026-105794 PUBLISHED

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.

• https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7
• 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
• https://github.com/microsoft/msquic/commit/a01333cf7c2659cce0ff03ef3f21e1ff15bb5b83
• https://github.com/microsoft/msquic/releases/tag/v2.4.20
• https://github.com/microsoft/msquic/releases/tag/v2.5.11
• https://github.com/microsoft/msquic/releases/tag/v2.6.1

• CWE-295: Improper Certificate Validation CWE