{"id":"CVE-2026-105794","aliases":["EUVD-2026-93422","GHSA-w5f4-fx9m-m4q7"],"status":"published","title":"MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL","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.","severity":{"version":"4.0","score":9.1,"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.01001,"percentile":0.63304,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-295"],"published":"2026-10-06T14:14:54Z","modified":"2026-10-28T11:03:45Z","fixes":[{"ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","fixed_in":["2.4.20","2.5.11","2.6.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.20"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.5.0"},{"fixed":"2.5.11"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.0"},{"fixed":"2.6.1"}]}]},{"source":"osv","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.20"}]}],"versions":["1.8.0"]},{"source":"osv","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.5.0"},{"fixed":"2.5.11"}]}]},{"source":"osv","ecosystem":"NuGet","package":"Microsoft.Native.Quic.MsQuic.OpenSSL","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.0"},{"fixed":"2.6.1"}]}]}],"products":[{"vendor":"microsoft","product":"msquic"}],"references":[{"url":"https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/microsoft/msquic/pull/6274","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/pull/6275","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/pull/6276","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/pull/6277","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/commit/0591586443cc73a2d2cfb679527d91a144b4a412","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/commit/508e811370df93e2ad848f5c78347d4fe4f65a91","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/commit/90fd45498bf9b506b8556fb407088688474d6c81","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/commit/a01333cf7c2659cce0ff03ef3f21e1ff15bb5b83","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/microsoft/msquic/releases/tag/v2.4.20","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/microsoft/msquic/releases/tag/v2.5.11","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/microsoft/msquic/releases/tag/v2.6.1","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-105794","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-w5f4-fx9m-m4q7"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/105xxx/CVE-2026-105794.json","tags":["advisory"]},{"url":"https://github.com/microsoft/msquic","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-105794","title":"MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL","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.","status":"published","published":"2026-10-06T14:14:54.483Z","modified":"2026-10-06T17:40:05.706Z","cvss":[{"version":"4.0","score":9.1,"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","level":"critical","assessor":"cna"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:19:56.755658Z"}],"euvd":[{"id":"EUVD-2026-93422","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.","status":"published","published":"2026-10-06T14:14:54Z","modified":"2026-10-06T17:40:05Z","cvss":[{"version":"4.0","score":9.1,"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","level":"critical"}],"updated_at":"2026-11-02T17:27:37.140631Z"}],"ghsa":[{"id":"GHSA-w5f4-fx9m-m4q7","title":"MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL","description":"# Summary\n\nImproper TLS hostname verification allows a man-in-the-middle (MITM) attack on MsQuic. \n\n# Details\n\nOnly MsQuic with the OpenSSL and QuicTLS TLS backends is affected (the Schannel backend is not affected).\n\n## Patches\n\n2.6.1, 2.5.11, and 2.4.20\n\n# Impact\n\nAn on-path attacker could spoof a server identity by using a certificate that doesn't match the intended target server hostname.","status":"published","published":"2026-10-06T15:33:08Z","modified":"2026-10-06T15:33:09Z","cvss":[{"version":"4.0","score":9.1,"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","level":"critical"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:41:27.036917Z"}],"nvd":[{"id":"CVE-2026-105794","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.","status":"published","published":"2026-10-06T15:17:16.26Z","modified":"2026-10-06T18:16:47.073Z","cvss":[{"version":"4.0","score":9.1,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T14:12:54.486849Z"}],"osv":[{"id":"CVE-2026-105794","title":"MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL","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.","status":"published","published":"2026-10-06T14:14:54.483Z","modified":"2026-10-28T11:03:45.237462819Z","cvss":[{"version":"4.0","score":9.1,"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","level":"critical"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T15:44:54.583213Z"},{"id":"GHSA-w5f4-fx9m-m4q7","title":"MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL","description":"# Summary\n\nImproper TLS hostname verification allows a man-in-the-middle (MITM) attack on MsQuic. \n\n# Details\n\nOnly MsQuic with the OpenSSL and QuicTLS TLS backends is affected (the Schannel backend is not affected).\n\n## Patches\n\n2.6.1, 2.5.11, and 2.4.20\n\n# Impact\n\nAn on-path attacker could spoof a server identity by using a certificate that doesn't match the intended target server hostname.","status":"published","published":"2026-10-06T15:33:08Z","modified":"2026-10-06T15:46:49.195357428Z","cvss":[{"version":"4.0","score":9.1,"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","level":"critical"}],"cwes":["CWE-295"],"updated_at":"2026-11-02T15:46:58.04805Z"}]}}