CVE-2026-96237 in .NET
Summary
by MITRE • 10/14/2026
Inclusion of functionality from untrusted control sphere in .NET allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves the inclusion of functionality originating from an untrusted control sphere within the Microsoft .NET framework, which creates a significant security risk by allowing remote attackers to execute arbitrary code over a network. This type of flaw typically stems from improper handling of serialized data or deserialization processes where objects are reconstructed without sufficient validation of their source or integrity. When a system accepts input from an untrusted entity and instantiates classes based on that input, it effectively grants the attacker control over the application's execution flow if they can manipulate the structure or content of the incoming data stream. This is particularly dangerous in web services, APIs, or any network-facing component that processes complex object graphs, as it bypasses standard access controls by leveraging legitimate framework mechanisms to perform unauthorized actions.
From a technical perspective, this issue aligns with CWE-502, which denotes Deserialization of Untrusted Data. The core flaw lies in the assumption that incoming data structures are safe and originate from trusted sources. In many .NET applications, developers may use serializers such as BinaryFormatter, XmlSerializer, or JSON converters without implementing strict allow-listing of expected types. An attacker can craft a malicious payload containing specially constructed objects that trigger side effects during deserialization, such as invoking dangerous methods, accessing sensitive memory regions, or initiating network connections to external command-and-control servers. This mechanism allows the execution of code with the privileges of the application process, potentially leading to full system compromise if the service runs with elevated permissions.
The operational impact of this vulnerability is severe, enabling remote code execution (RCE) without requiring user interaction or authentication in many scenarios. Once exploited, an attacker can escalate privileges, exfiltrate sensitive data, install malware, or use the compromised server as a pivot point for further attacks within the internal network. This aligns with MITRE ATT&CK technique T1059, Command and Scripting Interpreter, specifically when the executed code involves PowerShell or other scripting languages commonly available in Windows environments. Additionally, it relates to T1203, Exploitation for Client Execution, if the vulnerability is triggered via client-side components like web browsers accessing vulnerable endpoints. The ability to execute code over a network makes this one of the most critical categories of vulnerabilities, as it can be exploited at scale across distributed systems with minimal effort from the adversary.
Mitigation strategies must focus on strict input validation and secure deserialization practices. Developers should avoid using legacy serializers like BinaryFormatter for untrusted data entirely, opting instead for safer alternatives such as JSON.NET or System.Text.Json which do not support arbitrary object instantiation by default. If custom serialization is necessary, an allow-list approach should be implemented to restrict the types of objects that can be instantiated during deserialization. Furthermore, implementing integrity checks using digital signatures ensures that payloads have not been tampered with in transit. Network-level controls such as firewalls and intrusion detection systems can help monitor for anomalous traffic patterns associated with exploitation attempts, while regular security audits and static code analysis tools can identify instances of unsafe serialization calls within the codebase before deployment to production environments.