GHSA-4jxx-4qxw-prxm — Microsoft.AspNetCore.Sign…
HIGHGHSA-4jxx-4qxw-prxm is a high-severity (CVSS 7.5) CWE-19 vulnerability in Microsoft.AspNetCore.SignalR.Protocols.MessagePack. A fix is available for Microsoft.AspNetCore.SignalR.Protocols.MessagePack — see the affected versions and patch details below.
Denial of service 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
GHSA-4jxx-4qxw-prxm 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% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
Microsoft.AspNetCore.SignalR.Protocols.MessagePack.NETMicrosoft.AspNetCore.SignalR.Protocols.MessagePackReal-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 ASP.NET Core improperly handles web requests, aka 'ASP.NET Core Denial of Service Vulnerability'.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.AspNetCore.SignalR.Protocols.MessagePack | ≥ 1.1.0&&< 1.1.5 | 1.1.5dotnet add package Microsoft.AspNetCore.SignalR.Protocols.MessagePack --version 1.1.5 |
| .NETNuGet | Microsoft.AspNetCore.SignalR.Protocols.MessagePack | ≥ 1.0.0&&< 1.0.11 | 1.0.11dotnet add package Microsoft.AspNetCore.SignalR.Protocols.MessagePack --version 1.0.11 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.SignalR.Protocols.MessagePack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.SignalR.Protocols.MessagePack to 1.1.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4jxx-4qxw-prxm 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 GHSA-4jxx-4qxw-prxm can be triaged on real exposure rather than presence alone.
Tailored to GHSA-4jxx-4qxw-prxm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4jxx-4qxw-prxm in your dependencies?
O3 Security finds GHSA-4jxx-4qxw-prxm across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.