CVE-2017-8700
HIGHCVE-2017-8700 is a high-severity (CVSS 7.5) vulnerability in Microsoft.AspNetCore.Mvc.Core. O3 Security confirms whether CVE-2017-8700 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-origin Resource Sharing bypass in ASP.NET Core
Blast Radius
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 | 1.0.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Core | ≥ 1.1.0&&< 1.1.6 | 1.1.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Cors | ≥ 1.0.0&&< 1.0.6 | 1.0.6 |
| .NETNuGet | Microsoft.AspNetCore.Mvc.Cors | ≥ 1.1.0&&< 1.1.6 | 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 pinpoints whether CVE-2017-8700 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
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 detects CVE-2017-8700 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.