CVE-2026-70186 in ASP.NET Core
Summary
by MITRE • 10/14/2026
Deadlock in ASP.NET Core allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a denial of service condition within the ASP.NET Core framework, specifically manifesting as a deadlock scenario that can be triggered by external actors. This type of flaw typically arises from improper synchronization mechanisms or race conditions in how the web server handles concurrent requests. When an unauthorized attacker sends specific crafted network packets designed to exploit these synchronization points, they can cause threads responsible for processing HTTP requests to become permanently blocked waiting on resources held by other stalled threads. Because ASP.NET Core relies heavily on asynchronous I/O and thread pool management to handle high volumes of traffic efficiently, a deadlock effectively halts the progress of all dependent operations within that process or application domain.
From a technical perspective, this issue represents a failure in resource management where the system enters a state of circular dependency without any mechanism for recovery or timeout enforcement. The attacker does not need authentication credentials to exploit this flaw; rather, they leverage the network interface and the framework's request handling pipeline to induce the deadlock condition. This aligns with Common Weakness Enumeration (CWE) category CWE-833, which covers Deadlock conditions resulting from improper locking of shared resources. Furthermore, in terms of offensive security frameworks such as MITRE ATT&CK, this behavior falls under the Tactic Impact and specifically relates to techniques that disrupt availability, akin to resource exhaustion or service stop attacks like those categorized under TA0042.
The operational impact of this vulnerability is severe for any production environment running affected versions of ASP.NET Core. Once a deadlock occurs, the application becomes unresponsive to legitimate user requests until the process is manually restarted or the underlying operating system terminates it due to timeout policies. This results in complete service outage for all users accessing that specific endpoint or server instance. In high-availability architectures where multiple instances are behind a load balancer, this could lead to cascading failures if traffic is not properly rerouted away from the affected node before its health checks fail completely. The duration of the downtime depends on how long it takes for administrators to detect and restart the service, during which business operations may be significantly disrupted.
Mitigation strategies primarily involve applying vendor-provided patches that address the underlying synchronization logic within the ASP.NET Core runtime. Organizations should prioritize updating their .NET SDKs and runtimes to versions where this deadlock condition has been resolved through improved locking granularity or timeout implementations. In addition to patching, defensive measures include implementing rate limiting at the network perimeter to prevent a single source from overwhelming the server with concurrent requests that might trigger the race condition. Web Application Firewalls can also be configured to detect and block anomalous request patterns associated with this exploit vector. Regular security audits focusing on concurrency handling in custom middleware or controllers are recommended to ensure no similar vulnerabilities exist within application-specific code layers.