CVE-2026-105794: CWE-295: Improper Certificate Validation in microsoft msquic
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.
CVSS v4.0
Score 9.1critical
Affected software
microsoft
msquic
pkg:github/microsoft/msquicRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
MsQuic versions before 2.4.20, 2.5.11, and 2.6.1 have an improper certificate validation vulnerability (CWE-295) in clients using OpenSSL or QuicTLS TLS backends. These clients fail to verify that the server certificate matches the intended target hostname, allowing an attacker positioned on the network path to present a certificate that does not match the server's hostname and spoof the server in a man-in-the-middle attack. The Schannel TLS backend is unaffected. The vulnerability is resolved in MsQuic versions 2.4.20, 2.5.11, and 2.6.1.
Potential Impact
An attacker who can intercept network traffic (on-path) can exploit this vulnerability to spoof the intended server by presenting a certificate that does not match the target hostname. This can lead to man-in-the-middle attacks, potentially compromising confidentiality and integrity of communications. The vulnerability affects only MsQuic clients using OpenSSL or QuicTLS TLS backends; clients using the Schannel backend are not impacted.
Mitigation Recommendations
Upgrade MsQuic to version 2.4.20, 2.5.11, or 2.6.1 or later, where this certificate validation issue is fixed. No other mitigation is indicated. Since this is a client-side vulnerability, applying the official patches is the recommended remediation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-05T20:37:19.364Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ac506e32cdf04f656b9a05e
Added to database: 10/06/2026, 14:34:11 UTC
Last enriched: 10/06/2026, 14:48:33 UTC
Last updated: 10/06/2026, 21:42:15 UTC
Views: 13
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