CVE-2021-24111 in .NET Framework
Summary
by MITRE • 02/26/2021
.NET Framework Denial of Service Vulnerability
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Analysis
by VulDB Data Team • 06/29/2026
This vulnerability resides within the .NET Framework ecosystem and represents a critical denial of service condition that can be exploited by remote attackers to disrupt services. The flaw manifests when the framework fails to properly handle specific input sequences or malformed data structures during processing, leading to system instability and resource exhaustion. Attackers can leverage this weakness by sending carefully crafted requests that trigger abnormal program behavior, causing applications to crash or become unresponsive. The vulnerability impacts multiple versions of the .NET Framework across different operating systems and can affect various application types including web services, desktop applications, and server-side components. From a technical perspective, the issue stems from inadequate input validation mechanisms within the framework's core processing libraries, particularly in how they handle memory allocation and exception handling routines. The flaw allows attackers to consume excessive system resources or trigger infinite loops that prevent legitimate users from accessing services.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential business continuity issues and financial losses. Organizations running applications built on affected .NET Framework versions face significant risk of extended downtime, especially in mission-critical environments where availability is paramount. The vulnerability can be exploited through various attack vectors including web requests, API calls, or even internal network communications depending on the specific implementation details. Security teams must consider that this weakness can be combined with other exploits to create more sophisticated attack scenarios that may bypass traditional security controls. The flaw's exploitation typically requires minimal technical skill and can be automated using readily available tools, making it particularly dangerous for widespread deployment.
Mitigation strategies should focus on immediate patch application as provided by Microsoft security updates, which address the underlying code issues through proper input validation and resource management improvements. Organizations must implement comprehensive monitoring solutions to detect abnormal resource consumption patterns that may indicate exploitation attempts. Network segmentation and application firewalls can help limit the attack surface by restricting access to vulnerable components. Additionally, implementing proper input sanitization at multiple layers of the application architecture provides defense-in-depth protection against similar vulnerabilities. The vulnerability aligns with CWE-400 which specifically addresses uncontrolled resource consumption, and can be mapped to ATT&CK technique T1499 for network denial of service attacks. Organizations should also consider implementing rate limiting mechanisms and connection pooling configurations to reduce the impact of potential exploitation attempts. Regular security assessments and penetration testing help identify additional weaknesses that may compound the risk posed by this vulnerability in complex enterprise environments.