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This security vulnerability affects Microsoft.AspNetCore.SignalR.Common and Microsoft.AspNetCore.SignalR.Core components within .NET frameworks, specifically impacting stateful reconnect clients. In the architecture of ASP.NET Core SignalR, stateful reconnect features allow clients to temporarily disconnect and reconnect while attempting to resume their message stream. However, a flaw within the `MessageBuffer.ResendAsync` backpressure mechanism permits malicious or misbehaving clients to indefinitely block broadcast messages. Because resource allocation lacks strict bounding during these stuck backpressure states, associated memory and system handles are retained continuously. An unauthenticated attacker can exploit this behavior by manipulating reconnection streams to exhaust server resources. Consequently, this leads to a significant denial of service condition affecting all connected application users across Windows, Linux, and macOS environments. Remediating this issue requires updating affected .NET SDKs and runtimes to the latest patched versions followed by complete application restarts or recompilations.
DailyCVE Form:
Platform: Microsoft .NET
Version: All affected SDKs
Vulnerability : Resource Exhaustion
Severity: High
date: 10/13/2026
Prediction: Patch available now
What Undercode Say:
To verify the installed .NET information and locate vulnerable package references, administrators can run diagnostic commands directly within the environment shell.
dotnet --info dotnet list package --vulnerable
Developers must ensure that package versions mapping to Microsoft.AspNetCore.SignalR.Common and Microsoft.AspNetCore.SignalR.Core are upgraded immediately through NuGet package manager controls.
dotnet add package Microsoft.AspNetCore.SignalR.Common --version <patched_version> dotnet add package Microsoft.AspNetCore.SignalR.Core --version <patched_version>
Exploit: (Educational Purposes!)
An attacker initiates a stateful reconnection sequence against a vulnerable SignalR hub endpoint while intentionally stalling or failing to consume data frames through the stream buffer. By manipulating the flow control mechanisms governed by MessageBuffer.ResendAsync, the client forces the server-side buffer to wait indefinitely on backpressure signals. Since there are no proper throttling limits or timeout enforcement drops on the unacknowledged resend loops, the server retains all associated network buffers and connection contexts in memory. Repeating this action across multiple concurrent fake reconnect sessions quickly starves available server memory and worker threads, inducing a full denial of service for legitimate application users.
Protection: from this CVE
Defending against this vulnerability requires updating the underlying .NET runtime and SDK to the latest patched versions provided by Microsoft. If applications are deployed as self-contained packages, they must be fully recompiled with the updated SDK and redeployed to production environments. Developers should also review application monitoring configurations to detect abnormal memory retention or persistent connection bottlenecks tied to SignalR hubs.
Impact:
Successful exploitation results in a high-severity denial of service condition where the affected application server runs out of available memory and resources. This blocks all legitimate real-time message broadcasts and communication channels, causing total disruption for users relying on the ASP.NET Core SignalR infrastructure.
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Sources:
Reported By: github.com
Extra Source Hub:
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