CVE-2026-105794: MsQuic Improper Certificate Validation Vulnerability

CRITICAL
Advisory Identifier: GHSA-w5f4-fx9m-m4q7
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CWE-295
Published
Advisory Summary

CVE-2026-105794 is a CRITICAL improper certificate validation vulnerability (CWE-295: Improper Certificate Validation) affecting MsQuic libraries in the NuGet ecosystem. The issue involves improper certificate validation in microsoft.native.quic.msquic.openssl. Remediation is available by upgrading affected packages to version 2.4.20, 2.5.11, 2.6.1.

CVE-2026-105794 at a Glance

CVE Identifier CVE-2026-105794
GHSA Identifier GHSA-w5f4-fx9m-m4q7
Severity CRITICAL
CVSS v3.1 Base Score N/A
CWE Classification CWE-295: Improper Certificate Validation
Affected Product MsQuic
Package Ecosystem NuGet
Published Date
Last Updated

How to Fix CVE-2026-105794

To remediate this vulnerability, upgrade all affected MsQuic dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Microsoft.Native.Quic.MsQuic.OpenSSL fixed: 2.4.20 
Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to 2.4.20
Microsoft.Native.Quic.MsQuic.OpenSSL fixed: 2.5.11 
Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to 2.5.11
Microsoft.Native.Quic.MsQuic.OpenSSL fixed: 2.6.1 
Upgrade Microsoft.Native.Quic.MsQuic.OpenSSL to 2.6.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for Microsoft.Native.Quic.MsQuic.OpenSSL

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-105794, inspect your project dependencies for MsQuic:

inspect dependencies for Microsoft.Native.Quic.MsQuic.OpenSSL

Analyze the terminal output to locate any version of MsQuic in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.4.20), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-295: Improper Certificate Validation, where the product does not validate, or incorrectly validates, a certificate. In MsQuic, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

# Summary Improper TLS hostname verification allows a man-in-the-middle (MITM) attack on MsQuic. # Details Only MsQuic with the OpenSSL and QuicTLS TLS backends is affected (the Schannel backend is not affected). ## Patches 2.6.1, 2.5.11, and 2.4.20 # Impact An on-path attacker could spoof a server identity by using a certificate that doesn't match the intended target server hostname.

CVE-2026-105794 Affected MsQuic Versions

3 component(s)
Fixed Versions:
2.4.202.5.112.6.1
Product / Package Ecosystem Affected Versions Fixed Version
Microsoft.Native.Quic.MsQuic.OpenSSL
nuget/Microsoft.Native.Quic.MsQuic.OpenSSL
NuGet
< 2.4.20
2.4.20
Microsoft.Native.Quic.MsQuic.OpenSSL
nuget/Microsoft.Native.Quic.MsQuic.OpenSSL
NuGet
≥ 2.5.0
< 2.5.11
2.5.11
Microsoft.Native.Quic.MsQuic.OpenSSL
nuget/Microsoft.Native.Quic.MsQuic.OpenSSL
NuGet
≥ 2.6.0
< 2.6.1
2.6.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7
NVD — CVE-2026-105794 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-105794
MsQuic Source Repository REPOSITORY
https://github.com/microsoft/msquic/pull/6274
MsQuic Source Repository REPOSITORY
https://github.com/microsoft/msquic/pull/6275
MsQuic Source Repository REPOSITORY
https://github.com/microsoft/msquic/pull/6276
MsQuic Source Repository REPOSITORY
https://github.com/microsoft/msquic/pull/6277
Security Fix Commit FIX COMMIT
https://github.com/microsoft/msquic/commit/0591586443cc73a2d2cfb679527d91a144b4a412
Security Fix Commit FIX COMMIT
https://github.com/microsoft/msquic/commit/508e811370df93e2ad848f5c78347d4fe4f65a91
Security Fix Commit FIX COMMIT
https://github.com/microsoft/msquic/commit/90fd45498bf9b506b8556fb407088688474d6c81
Security Fix Commit FIX COMMIT
https://github.com/microsoft/msquic/commit/a01333cf7c2659cce0ff03ef3f21e1ff15bb5b83
MsQuic Source Repository REPOSITORY
https://github.com/microsoft/msquic
MsQuic Release RELEASE
https://github.com/microsoft/msquic/releases/tag/v2.4.20
MsQuic Release RELEASE
https://github.com/microsoft/msquic/releases/tag/v2.5.11
MsQuic Release RELEASE
https://github.com/microsoft/msquic/releases/tag/v2.6.1

Frequently Asked Questions

What is CVE-2026-105794?
CVE-2026-105794 is a security vulnerability in MsQuic involving Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL under CWE-295: Improper Certificate Validation.
Which MsQuic versions are affected?
Affected versions include releases prior to 2.4.20, 2.5.11, 2.6.1 across affected packages: Microsoft.Native.Quic.MsQuic.OpenSSL.
What version fixes CVE-2026-105794?
Upgrading to 2.4.20, 2.5.11, 2.6.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Microsoft.Native.Quic.MsQuic.OpenSSL affected?
Yes, Microsoft.Native.Quic.MsQuic.OpenSSL is affected in releases prior to 2.4.20, 2.5.11, 2.6.1. Upgrade your dependency to 2.4.20, 2.5.11, 2.6.1 or later.
What CWE is associated with CVE-2026-105794?
CVE-2026-105794 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check NuGet dependencies for CVE-2026-105794?
Run the dependency tree command: 'inspect dependencies for Microsoft.Native.Quic.MsQuic.OpenSSL'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w5f4-fx9m-m4q7",
  "modified" : "2026-10-06T15:33:08Z",
  "published" : "2026-10-06T15:33:08Z",
  "aliases" : [ "CVE-2026-105794" ],
  "summary" : "MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL",
  "details" : "# 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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
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    },
    "ranges" : [ {
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      "events" : [ {
        "introduced" : "0"
      }, {
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      } ]
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  }, {
    "package" : {
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    } ]
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    },
    "ranges" : [ {
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        "introduced" : "2.6.0"
      }, {
        "fixed" : "2.6.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7"
  }, {
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    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-105794"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/pull/6274"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/pull/6275"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/pull/6276"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/pull/6277"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/commit/0591586443cc73a2d2cfb679527d91a144b4a412"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/commit/508e811370df93e2ad848f5c78347d4fe4f65a91"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/commit/90fd45498bf9b506b8556fb407088688474d6c81"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/commit/a01333cf7c2659cce0ff03ef3f21e1ff15bb5b83"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/microsoft/msquic"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/releases/tag/v2.4.20"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/releases/tag/v2.5.11"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/msquic/releases/tag/v2.6.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-06T15:33:08Z",
    "nvd_published_at" : "2026-10-06T15:17:16Z"
  }
}