What’s Vulnerable › Vulnerabilities

CVE-2026-105794: MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL

• Severity: critical (CVSS 9.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-06 · updated 2026-10-06
• Weakness: CWE-295

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.

Affected products

• microsoft msquic: before 2.4.20; from 2.5.0, < 2.5.11; from 2.6.0, < 2.6.1

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
• 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/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
• https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7

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