CVE-2017-11883 in ASP.NET
Summary
by MITRE
.NET Core 1.0, 1.1, and 2.0 allow an unauthenticated attacker to remotely cause a denial of service attack against a .NET Core web application by improperly handling web requests, aka ".NET CORE Denial Of Service Vulnerability".
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/23/2021
The vulnerability identified as CVE-2017-11883 represents a critical denial of service weakness affecting multiple versions of Microsoft .NET Core framework including 1.0, 1.1, and 2.0. This flaw exists within the web request handling mechanisms of the framework, creating an avenue for unauthenticated remote attackers to disrupt service availability. The vulnerability stems from improper validation and processing of incoming web requests that can be exploited without requiring any authentication credentials or privileged access. The attack vector specifically targets the core request processing pipeline where malformed or specially crafted requests can trigger unexpected behavior in the application runtime. This issue falls under the category of CWE-400, which encompasses weaknesses related to resource management and denial of service conditions. The vulnerability demonstrates a fundamental flaw in input validation and request handling that can be leveraged by attackers to consume excessive system resources or cause application crashes.
The technical implementation of this vulnerability exploits the way .NET Core applications process incoming HTTP requests through their web hosting pipeline. When a malformed request is received, the framework's request parsing and routing components fail to properly handle the unexpected input, leading to resource exhaustion or application instability. The flaw likely manifests during the request deserialization process where the framework attempts to interpret request data without adequate bounds checking or input sanitization. Attackers can craft specific request patterns that cause the application to enter infinite loops, consume excessive memory, or trigger unhandled exceptions that result in service termination. The vulnerability's impact extends beyond simple application crashes to include complete service unavailability, making it particularly dangerous in production environments where continuous availability is critical. This weakness aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and represents a classic example of how improper input handling can lead to system instability.
The operational impact of CVE-2017-11883 is substantial for organizations running affected .NET Core applications, as it provides attackers with a straightforward method to disrupt services without requiring any advanced technical skills or credentials. The vulnerability can be exploited at scale, potentially affecting multiple applications simultaneously if they share common infrastructure or deployment patterns. Organizations may experience significant downtime, revenue loss, and customer impact when services become unavailable due to this attack vector. The attack can be executed remotely from any location with network access to the affected systems, making it particularly challenging to defend against. The vulnerability's presence in multiple versions of .NET Core means that organizations must carefully assess their deployment environments and ensure all affected components are updated. Additionally, the lack of authentication requirements means that even basic network monitoring and access controls may not prevent exploitation, requiring more robust application-level protections and proactive patch management.
Mitigation strategies for this vulnerability center on immediate patching and application hardening measures. Microsoft released security updates for all affected .NET Core versions, and organizations should prioritize applying these patches to eliminate the vulnerability. System administrators should implement network-level protections such as rate limiting and request filtering to reduce the impact of potential attacks while patches are being deployed. Application-level protections include implementing request validation middleware that can detect and reject malformed requests before they reach core processing components. Organizations should also consider deploying web application firewalls that can identify and block suspicious request patterns associated with this vulnerability. Monitoring and alerting systems should be enhanced to detect unusual request patterns or resource consumption spikes that may indicate exploitation attempts. The remediation process should include thorough testing of patched applications to ensure that the security updates do not introduce compatibility issues or regressions. Long-term defense strategies should emphasize robust input validation practices and regular security assessments of web applications to identify similar vulnerabilities in other components of the application stack.