CVE-2025-55315
CRITICALCVE-2025-55315 is a critical-severity (CVSS 9.9) CWE-444 vulnerability in Microsoft.AspNetCore.Server.Kestrel.Core. 3 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2025-55315 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability
Blast Radius
Microsoft.AspNetCore.Server.Kestrel.Core.NETMicrosoft.AspNetCore.App.Runtime.linux-arm.NETMicrosoft.AspNetCore.App.Runtime.linux-arm64.NETMicrosoft.AspNetCore.App.Runtime.linux-musl-arm.NETMicrosoft.AspNetCore.App.Runtime.linux-musl-arm64.NETMicrosoft.AspNetCore.App.Runtime.linux-musl-x64.NETMicrosoft.AspNetCore.App.Runtime.linux-x64.NETMicrosoft.AspNetCore.App.Runtime.osx-arm64+29 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
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.AspNetCore.Server.Kestrel.Core | all versions | 2.3.6 |
| .NETNuGet | Microsoft.AspNetCore.App.Runtime.linux-arm | ≥ 10.0.0-rc.1.25451.107&&< 10.0.0-rc.2.25502.107 | 10.0.0-rc.2.25502.107 |
| .NETNuGet | Microsoft.AspNetCore.App.Runtime.linux-arm64 | ≥ 10.0.0-rc.1.25451.107&&< 10.0.0-rc.2.25502.107 | 10.0.0-rc.2.25502.107 |
| .NETNuGet | Microsoft.AspNetCore.App.Runtime.linux-musl-arm | ≥ 10.0.0-rc.1.25451.107&&< 10.0.0-rc.2.25502.107 | 10.0.0-rc.2.25502.107 |
| .NETNuGet | Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | ≥ 10.0.0-rc.1.25451.107&&< 10.0.0-rc.2.25502.107 | 10.0.0-rc.2.25502.107 |
| .NETNuGet | Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | ≥ 10.0.0-rc.1.25451.107&&< 10.0.0-rc.2.25502.107 | 10.0.0-rc.2.25502.107 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
ASP.net 8.0.10 - Bypass
by Mohammed Idrees Banyamer · Apr 6, 2026
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.Server.Kestrel.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.Server.Kestrel.Core to 2.3.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-55315 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-2025-55315 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-2025-55315. 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-2025-55315 in your dependencies?
O3 detects CVE-2025-55315 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.