How severe is GHSA-w5f4-fx9m-m4q7?

No CVSS score has been assigned to GHSA-w5f4-fx9m-m4q7 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-w5f4-fx9m-m4q7?

GHSA-w5f4-fx9m-m4q7 affects the following packages: Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet), Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet), Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet). Ecosystems affected: NuGet.

How do I fix GHSA-w5f4-fx9m-m4q7?

Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.4.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w5f4-fx9m-m4q7 is resolved across your whole dependency graph.

How do I detect GHSA-w5f4-fx9m-m4q7 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.Native.Quic.MsQuic.OpenSSL, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-w5f4-fx9m-m4q7 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-w5f4-fx9m-m4q7 actively exploited in the wild?

No public exploit code has been indexed for GHSA-w5f4-fx9m-m4q7 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-w5f4-fx9m-m4q7?

GHSA-w5f4-fx9m-m4q7 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 62th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-w5f4-fx9m-m4q7?

GHSA-w5f4-fx9m-m4q7 is classified as CWE-295 (CWE-295). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-w5f4-fx9m-m4q7 published, and has it been updated?

GHSA-w5f4-fx9m-m4q7 was published on October 6, 2026 and was last updated on October 6, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET NuGet

Not in CISA KEV

MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSLGHSA-w5f4-fx9m-m4q7

Fix: microsoft/msquic#6274

GHSA-w5f4-fx9m-m4q7 is a CWE-295 vulnerability in Microsoft.Native.Quic.MsQuic.OpenSSL. A fix is available for Microsoft.Native.Quic.MsQuic.OpenSSL — see the affected versions and patch details below.

Also known asCVE-2026-105794

Published

Oct 6, 2026

Updated

Oct 6, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs62th percentile — riskier than 62% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

3 pkgs affected

.NETMicrosoft.Native.Quic.MsQuic.OpenSSL.NETMicrosoft.Native.Quic.MsQuic.OpenSSL.NETMicrosoft.Native.Quic.MsQuic.OpenSSL

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

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

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Microsoft.Native.Quic.MsQuic.OpenSSL`	all versions	2.4.20`dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.4.20`
.NETNuGet	`Microsoft.Native.Quic.MsQuic.OpenSSL`	≥ 2.5.0&&< 2.5.11	2.5.11`dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.5.11`
.NETNuGet	`Microsoft.Native.Quic.MsQuic.OpenSSL`	≥ 2.6.0&&< 2.6.1	2.6.1`dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.6.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.Native.Quic.MsQuic.OpenSSL, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.4.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w5f4-fx9m-m4q7 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

# 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.