---
title: "CVE-2026-105794: MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL"
url: https://erroneo.us/security/cve/CVE-2026-105794/
description: "CVE-2026-105794 (Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet)): MsQuic is a cross-platform C implementation of the IETF QUIC protocol exposed to C, C++, C#…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-06
date_modified: 2026-10-06
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-105794"
kev: false
cvss: 9.1
epss: 0.01001
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-105794: MsQuic: Improper Certificate Validation in Microsoft.Native.Quic.MsQuic.OpenSSL

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 1.0% , percentile 62: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 62% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet) < 2.4.20, fixed in 2.4.20 ; Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet) >= 2.5.0, < 2.5.11, fixed in 2.5.11 ; Microsoft.Native.Quic.MsQuic.OpenSSL (NuGet) >= 2.6.0, < 2.6.1, fixed in 2.6.1 . Check your lockfile, including transitive dependencies.

## What it 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.

## Affected packages

- NuGet `Microsoft.Native.Quic.MsQuic.OpenSSL` < 2.4.20 → fixed: 2.4.20
- NuGet `Microsoft.Native.Quic.MsQuic.OpenSSL` >= 2.5.0, < 2.5.11 → fixed: 2.5.11
- NuGet `Microsoft.Native.Quic.MsQuic.OpenSSL` >= 2.6.0, < 2.6.1 → fixed: 2.6.1

## Affected products (CVE record)

- microsoft msquic: < 2.4.20, >= 2.5.0, < 2.5.11, >= 2.6.0, < 2.6.1

## Severity

- GitHub_M CVSS 4.0: 9.1 `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`
- GitHub CVSS 4.0: 9.1 `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`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 1.00% probability of exploitation activity in the next 30 days; percentile 62.

## Sources

- [GitHub Advisory GHSA-w5f4-fx9m-m4q7](https://github.com/advisories/GHSA-w5f4-fx9m-m4q7)
- [CVE.org record CVE-2026-105794](https://www.cve.org/CVERecord?id=CVE-2026-105794)
- [NVD entry CVE-2026-105794](https://nvd.nist.gov/vuln/detail/CVE-2026-105794)
- [github.com](https://github.com/microsoft/msquic/security/advisories/GHSA-w5f4-fx9m-m4q7)
- [github.com](https://github.com/microsoft/msquic/pull/6274)
- [github.com](https://github.com/microsoft/msquic/pull/6275)
- [github.com](https://github.com/microsoft/msquic/pull/6276)
- [github.com](https://github.com/microsoft/msquic/pull/6277)
- [github.com](https://github.com/microsoft/msquic/commit/0591586443cc73a2d2cfb679527d91a144b4a412)
- [github.com](https://github.com/microsoft/msquic/commit/508e811370df93e2ad848f5c78347d4fe4f65a91)
- [github.com](https://github.com/microsoft/msquic/commit/90fd45498bf9b506b8556fb407088688474d6c81)
- [github.com](https://github.com/microsoft/msquic/commit/a01333cf7c2659cce0ff03ef3f21e1ff15bb5b83)
- [github.com](https://github.com/microsoft/msquic/releases/tag/v2.4.20)
- [github.com](https://github.com/microsoft/msquic/releases/tag/v2.5.11)
- [github.com](https://github.com/microsoft/msquic/releases/tag/v2.6.1)

---
Source page: https://erroneo.us/security/cve/CVE-2026-105794/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt