Microsoft MsQuic up to 2.4.19/2.5.10/2.6.0 OpenSSL/QuicTLS TLS backend certificate validation

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Microsoft MsQuic up to 2.4.19/2.5.10/2.6.0. Affected is an unknown function of the component OpenSSL/QuicTLS TLS backend. Performing a manipulation results in certificate validation. This vulnerability was named CVE-2026-105794. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Microsoft MsQuic up to 2.4.19/2.5.10/2.6.0. It has been classified as problematic. This affects an unknown functionality of the component OpenSSL/QuicTLS TLS backend. The manipulation with an unknown input leads to a certificate validation vulnerability. CWE is classifying the issue as CWE-295. The product does not validate, or incorrectly validates, a certificate. This is going to have an impact on integrity. The summary by CVE 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 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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-105794 since 10/05/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/06/2026). The attack technique deployed by this issue is T1587.003 according to MITRE ATT&CK.

Upgrading to version 2.4.20, 2.5.11 or 2.6.1 eliminates this vulnerability.

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Productinfo

Vendor

• Microsoft

Name

• MsQuic

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.4.0
• 2.4.1
• 2.4.2
• 2.4.3
• 2.4.4
• 2.4.5
• 2.4.6
• 2.4.7
• 2.4.8
• 2.4.9
• 2.4.10
• 2.4.11
• 2.4.12
• 2.4.13
• 2.4.14
• 2.4.15
• 2.4.16
• 2.4.17
• 2.4.18
• 2.4.19
• 2.5
• 2.5.0
• 2.5.1
• 2.5.2
• 2.5.3
• 2.5.4
• 2.5.5
• 2.5.6
• 2.5.7
• 2.5.8
• 2.5.9
• 2.5.10
• 2.6.0

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://github.com/microsoft/msquic/

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