CVE-2017-0247 — Microsoft.AspNetCore.Mvc
HIGHCVE-2017-0247 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in Microsoft.AspNetCore.Mvc. 1 public exploit reference exists, so weaponization risk is real. A fix is available for Microsoft.AspNetCore.Mvc — see the affected versions and patch details below.
ASP.NET Core fails to properly validate web requests
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2017-0247 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
Microsoft.AspNetCore.Mvc.NETMicrosoft.AspNetCore.Mvc.NETMicrosoft.AspNetCore.Mvc.Core.NETMicrosoft.AspNetCore.Mvc.Core.NETSystem.Net.Http.NETSystem.Net.Http.NETSystem.Text.Encodings.Web.NETSystem.Text.Encodings.Web+30 moreReal-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 denial of service vulnerability exists when the ASP.NET Core fails to properly validate web requests. NOTE: Microsoft has not commented on third-party claims that the issue is that the TextEncoder.EncodeCore function in the System.Text.Encodings.Web package in ASP.NET Core Mvc before 1.0.4 and 1.1.x before 1.1.3 allows remote attackers to cause a denial of service by leveraging failure to properly calculate the length of 4-byte characters in the Unicode Non-Character range.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.AspNetCore.Mvc | ≥ 1.0.0&&< 1.0.4 | 1.0.4dotnet add package Microsoft.AspNetCore.Mvc --version 1.0.4 |
| .NETNuGet | Microsoft.AspNetCore.Mvc | ≥ 1.1.0&&< 1.1.3 | 1.1.3dotnet add package Microsoft.AspNetCore.Mvc --version 1.1.3 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Core | ≥ 1.0.0&&< 1.0.4 | 1.0.4dotnet add package Microsoft.AspNetCore.Mvc.Core --version 1.0.4 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Core | ≥ 1.1.0&&< 1.1.3 | 1.1.3dotnet add package Microsoft.AspNetCore.Mvc.Core --version 1.1.3 |
| .NETNuGet | System.Net.Http | ≥ 4.1.1&&< 4.1.2 | 4.1.2dotnet add package System.Net.Http --version 4.1.2 |
| .NETNuGet | System.Net.Http | ≥ 4.3.1&&< 4.3.2 | 4.3.2dotnet add package System.Net.Http --version 4.3.2 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.Mvc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.Mvc to 1.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-0247 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2017-0247 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2017-0247. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2017-0247 in your dependencies?
O3 Security finds CVE-2017-0247 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.