CVE-2026-105794

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.

CVSS 4.0

9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS

1.0% chance of exploitation in the next 30 days; higher than 62% of CVEs (scores of 2026-10-25)

CWE

CWE-295

Published

2026-10-06

Modified

2026-10-06

Record from

the NVD, synced 2026-10-19

References

• 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/pull/6274

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