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.NET
.NET NuGet
Not in CISA KEV
MEDIUM severity

CVE-2019-0657 — Microsoft.NETCore.App

MEDIUM

CVE-2019-0657 is a medium-severity (CVSS 5.9) Improper Input Validation vulnerability in Microsoft.NETCore.App. A fix is available for Microsoft.NETCore.App — see the affected versions and patch details below.

Improper Input Validation in .Net Framework API's

Also known asGHSA-x5qj-9vmx-7g6g
Published
Updated
Affected
3 pkgs
Patched
3 / 3
Exploits
None indexed
Exploitation data as of Oct 30, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
4.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs92th percentile — riskier than 92% of all scored CVEsHighest risk
3.47%5.33%7.20%9.07%8.0%4.5%May 26Aug 26Oct 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected
.NETMicrosoft.NETCore.App.NETMicrosoft.NETCore.App.NETSystem.Private.Uri

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

A vulnerability exists in certain .Net Framework API's and Visual Studio in the way they parse URL's, aka '.NET Framework and Visual Studio Spoofing Vulnerability'.

Affected Packages

3 total 3 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetMicrosoft.NETCore.App≥ 2.2.0&&< 2.2.22.2.2dotnet add package Microsoft.NETCore.App --version 2.2.2
.NETNuGetMicrosoft.NETCore.App≥ 2.1.0&&< 2.1.82.1.8dotnet add package Microsoft.NETCore.App --version 2.1.8
.NETNuGetSystem.Private.Uri≥ 4.3.0&&< 4.3.24.3.2dotnet add package System.Private.Uri --version 4.3.2

Affected Products

4 products · 32 configurations
Application
.net coremicrosoft
3 versions
1.02.12.2
Application
.net frameworkmicrosoft
11 versions
2.03.03.53.5.14.5.24.64.6.14.6.24.74.7.14.7.2
Application
powershell coremicrosoft
2 versions
6.06.1
Application
visual studio 2017microsoft
1 version
15.9

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.NETCore.App, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update Microsoft.NETCore.App to 2.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-0657 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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate
ProductFixed inAdvisory
.NET Core on Red Hat Enterprise Linuxrh-dotnet21-0:2.1-7.el7RHSA-2019:0349

Frequently Asked Questions

A vulnerability exists in certain .Net Framework API's and Visual Studio in the way they parse URL's, aka '.NET Framework and Visual Studio Spoofing Vulnerability'.
O3 Security · Impact-Aware SCA

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CVE-2019-0657: Microsoft.NETCore.App — Fixed in 2.2.2