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CRITICAL severity

CVE-2026-32179 — Microsoft.Native.Quic.MsQ…

CRITICALFix: microsoft/msquic@1e6e999

CVE-2026-32179 is a critical-severity (CVSS 9.8) 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.

MsQuic has a Remote Elevation of Privilege Vulnerability

Published
Updated
Affected
4 pkgs
Patched
4 / 4
Exploits
None indexed
Exploitation data as of May 8, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

4 pkgs affected
.NETMicrosoft.Native.Quic.MsQuic.OpenSSL.NETMicrosoft.Native.Quic.MsQuic.Schannel.NETMicrosoft.Native.Quic.MsQuic.Schannel.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

Summary

Improper input validation in Microsoft QUIC allows an unauthorized attacker to elevate privileges over a network.

Details

Improper Input Validation Integer Underflow (Wrap or Wraparound) when decoding ACK frame.

Patches

  • Fix underflow in ACK frame parsing - 1e6e999b

Impact

An attacker who successfully exploited this vulnerability could gain elevated privileges.

Affected Packages

4 total 4 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetMicrosoft.Native.Quic.MsQuic.OpenSSL≥ 2.5.0-ci.532574&&< 2.5.72.5.7dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.5.7
.NETNuGetMicrosoft.Native.Quic.MsQuic.Schannel≥ 2.5.0-ci.532574&&< 2.5.72.5.7dotnet add package Microsoft.Native.Quic.MsQuic.Schannel --version 2.5.7
.NETNuGetMicrosoft.Native.Quic.MsQuic.Schannelall versions2.4.18dotnet add package Microsoft.Native.Quic.MsQuic.Schannel --version 2.4.18
.NETNuGetMicrosoft.Native.Quic.MsQuic.OpenSSLall versions2.4.18dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.4.18

Detection & mitigation playbook

Open-source dependency

  1. 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.

  2. Fix

    Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.5.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-32179 is resolved across your whole dependency graph.

  3. 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 input validation in Microsoft QUIC allows an unauthorized attacker to elevate privileges over a network. ### Details Improper Input Validation Integer Underflow (Wrap or Wraparound) when decoding ACK frame. #### Patches - Fix underflow in ACK frame parsing - 1e6e999b ### Impact An attacker who successfully exploited this vulnerability could gain elevated privileges.
O3 Security · Impact-Aware SCA

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