CVE-2026-70159: Microsoft Security Advisory CVE-2026-70159 - ASP.NET Core Denial of Service Vulnerability

October 13, 2026

Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.SignalR.Common and Microsoft.AspNetCore.SignalR.Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

SignalR stateful reconnect clients can indefinitely block broadcasts through MessageBuffer.ResendAsync backpressure and retain associated resources.

References

github.com/advisories/GHSA-334f-vvp4-7g6p
github.com/dotnet/announcements/issues/452
github.com/dotnet/aspnetcore/discussions/69792
github.com/dotnet/aspnetcore/security/advisories/GHSA-334f-vvp4-7g6p
nvd.nist.gov/vuln/detail/CVE-2026-70159

Code Behaviors & Features

Detect and mitigate CVE-2026-70159 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Dependency Scanning using SBOM also detects vulnerabilities from proprietary advisories that this site does not include. Learn more about Dependency Scanning using SBOM →