CVE-2023-21722 in .NET Framework
Summary
by MITRE • 02/14/2023
.NET Framework Denial of Service Vulnerability
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Analysis
by VulDB Data Team • 03/15/2023
The CVE-2023-21722 vulnerability represents a critical denial of service weakness within the Microsoft .NET Framework that affects multiple versions of the runtime environment. This vulnerability stems from improper handling of specific input data structures during the processing of certain .NET Framework operations, creating a condition where maliciously crafted inputs can cause the affected applications to consume excessive system resources or terminate unexpectedly. The flaw specifically impacts applications that utilize the .NET Framework's reflection and serialization capabilities, making it particularly dangerous in enterprise environments where these components are extensively deployed.
The technical root cause of this vulnerability lies in the way the .NET Framework handles object deserialization and type resolution during runtime execution. When applications process untrusted input through the framework's serialization mechanisms, particularly involving complex object graphs and type information, the runtime fails to properly validate the depth and complexity of the data structures being processed. This leads to a situation where an attacker can craft input that causes the deserialization process to enter infinite loops or consume excessive memory resources, ultimately resulting in system instability and denial of service conditions. The vulnerability is categorized under CWE-400, which specifically addresses "Uncontrolled Resource Consumption" and falls within the broader category of resource exhaustion attacks that target application processing logic.
The operational impact of CVE-2023-21722 extends beyond simple service disruption to potentially compromise entire application stacks and infrastructure availability. Organizations running .NET Framework applications that handle external input or process serialized data from untrusted sources face significant risk of system-wide outages, particularly in scenarios involving web applications, API endpoints, or services that deserialize user-provided data. Attackers can exploit this vulnerability through various vectors including HTTP requests, file uploads, or network communications that pass through affected .NET applications. The vulnerability's exploitation requires minimal privileges and can be executed remotely, making it particularly attractive to threat actors seeking to disrupt services without requiring extensive system access. This aligns with ATT&CK technique T1499.004, which covers "Evasion: Network Denial of Service" and demonstrates how resource exhaustion can be leveraged to achieve service disruption.
Mitigation strategies for CVE-2023-21722 must address both immediate protection and long-term architectural improvements to prevent exploitation. Microsoft has released security updates that patch the vulnerability by implementing proper input validation and resource limits during deserialization operations. Organizations should prioritize applying these patches immediately to all affected systems, particularly those running .NET Framework versions prior to the patched releases. Additional defensive measures include implementing input validation controls, limiting serialization capabilities in applications, and deploying application firewalls or intrusion detection systems that can monitor for suspicious deserialization patterns. The implementation of rate limiting and resource quotas can help prevent exploitation attempts from exhausting system resources, while code reviews and security testing should focus on identifying areas where untrusted data is processed through serialization mechanisms. Organizations should also consider implementing network segmentation and monitoring solutions to detect potential exploitation attempts and maintain audit trails for forensic analysis.