CVE-2017-8700 — Microsoft.AspNetCore.Mvc.…
HIGHCVE-2017-8700 is a high-severity (CVSS 7.5) vulnerability in Microsoft.AspNetCore.Mvc.Core. EPSS puts its 30-day exploitation probability at 10.5% (96th percentile). A fix is available for Microsoft.AspNetCore.Mvc.Core — see the affected versions and patch details below.
Cross-origin Resource Sharing bypass in ASP.NET Core
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-2017-8700 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.Core.NETMicrosoft.AspNetCore.Mvc.Core.NETMicrosoft.AspNetCore.Mvc.Cors.NETMicrosoft.AspNetCore.Mvc.CorsReal-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
ASP.NET Core 1.0, 1.1, and 2.0 allow an attacker to bypass Cross-origin Resource Sharing (CORS) configurations and retrieve normally restricted content from a web application, aka "ASP.NET Core Information Disclosure Vulnerability".
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.AspNetCore.Mvc.Core | ≥ 1.0.0&&< 1.0.6 | 1.0.6dotnet add package Microsoft.AspNetCore.Mvc.Core --version 1.0.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Core | ≥ 1.1.0&&< 1.1.6 | 1.1.6dotnet add package Microsoft.AspNetCore.Mvc.Core --version 1.1.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Cors | ≥ 1.0.0&&< 1.0.6 | 1.0.6dotnet add package Microsoft.AspNetCore.Mvc.Cors --version 1.0.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Cors | ≥ 1.1.0&&< 1.1.6 | 1.1.6dotnet add package Microsoft.AspNetCore.Mvc.Cors --version 1.1.6 |
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.Core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.Mvc.Core to 1.0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-8700 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-2017-8700 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2017-8700. 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-2017-8700 in your dependencies?
O3 Security finds CVE-2017-8700 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.