CVE-2018-8171 — Microsoft.AspNetCore.Iden…
HIGHCVE-2018-8171 is a high-severity (CVSS 7.5) Improper Authentication vulnerability in Microsoft.AspNetCore.Identity. EPSS puts its 30-day exploitation probability at 10.5% (96th percentile). A fix is available for Microsoft.AspNetCore.Identity — see the affected versions and patch details below.
Security feature bypass vulnerability exists in ASP.NET when the number of incorrect login attempts is not validated
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-2018-8171 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 378,567 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.Identity.NETMicrosoft.AspNetCore.Identity.NETMicrosoft.AspNetCore.Identity.NETMicrosoft.AspNetCore.IdentityReal-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 Security Feature Bypass vulnerability exists in ASP.NET when the number of incorrect login attempts is not validated, aka "ASP.NET Security Feature Bypass Vulnerability." This affects ASP.NET, ASP.NET Core 1.1, ASP.NET Core 1.0, ASP.NET Core 2.0, ASP.NET MVC 5.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.AspNetCore.Identity | ≥ 1.0.0&&< 1.0.6 | 1.0.6dotnet add package Microsoft.AspNetCore.Identity --version 1.0.6 |
| .NETNuGet | Microsoft.AspNetCore.Identity | ≥ 1.1.0&&< 1.1.6 | 1.1.6dotnet add package Microsoft.AspNetCore.Identity --version 1.1.6 |
| .NETNuGet | Microsoft.AspNetCore.Identity | ≥ 2.0.0&&< 2.0.4 | 2.0.4dotnet add package Microsoft.AspNetCore.Identity --version 2.0.4 |
| .NETNuGet | Microsoft.AspNetCore.Identity | ≥ 2.1.0&&< 2.1.2 | 2.1.2dotnet add package Microsoft.AspNetCore.Identity --version 2.1.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.Identity, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.Identity to 1.0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-8171 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-2018-8171 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2018-8171. 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-2018-8171 in your dependencies?
O3 Security finds CVE-2018-8171 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.