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Vulnerability · Published Oct 6, 2026 · Assigned by GitHub_M

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

Critical 9.1

In plain English

A critical-severity improper certificate validation in msquic from microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 63% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)9.1Critical
Exploit odds (30 days)1.0%top 37.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
NuGetmicrosoft.native.quic.msquic.openssl2.4.20GHSA-w5f4-fx9m-m4q7
NuGetmicrosoft.native.quic.msquic.openssl2.5.11GHSA-w5f4-fx9m-m4q7
NuGetmicrosoft.native.quic.msquic.openssl2.6.1GHSA-w5f4-fx9m-m4q7

Affected products (as reported)

VendorProductVersions
microsoft msquic < 2.4.20>= 2.5.0, < 2.5.11>= 2.6.0, < 2.6.1

Weakness: CWE-295 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References