CVE-2026-97801 in .NET Framework
Summary
by MITRE • 10/15/2026
Improper validation of specified type of input in .NET Framework allows an unauthorized attacker to perform tampering over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described involves a critical flaw within the Microsoft .NET Framework, specifically concerning the improper validation of specific types of user-supplied input data. This security weakness stems from insufficient sanitization or type-checking mechanisms during the processing of incoming requests, which allows an attacker to inject malicious payloads that bypass expected constraints. In many cases, this relates to how serialized objects or configuration parameters are deserialized and interpreted by the framework's runtime environment. When the system fails to rigorously validate the structure, content, or origin of these inputs before execution, it creates a pathway for unauthorized manipulation of application logic or underlying system resources. This lack of strict input validation is a fundamental design error that undermines the integrity of the software processing pipeline.
From an operational perspective, this flaw enables remote attackers to perform tampering over a network without requiring prior authentication in many scenarios. By exploiting the improper validation, an attacker can alter data streams, modify application state, or potentially execute arbitrary code depending on the specific context and privileges granted to the affected process. The impact is severe because it compromises both the confidentiality and integrity of the system. Attackers can manipulate business logic, steal sensitive information by altering query parameters, or escalate their access levels within the network infrastructure. This type of vulnerability often leads to broader security breaches as it serves as an entry point for more complex attacks such as SQL injection, cross-site scripting, or remote code execution if the tampered input triggers unsafe operations within the framework.
This issue aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-20 Improper Input Validation and CWE-502 Deserialization of Untrusted Data, depending on whether the flaw occurs during general parameter processing or specifically during object deserialization. In terms of the MITRE ATT&CK framework, this vulnerability facilitates techniques related to Initial Access via Exploitation for Client Execution if it leads to code execution, or Defense Evasion through Obfuscated Inputs if attackers use encoding to bypass detection mechanisms. The ability to tamper with network traffic implies that the attacker can manipulate the communication between clients and servers, potentially leading to session hijacking or data integrity violations across distributed systems relying on this framework version.
To mitigate these risks, organizations must ensure that all .NET Framework installations are updated to the latest security patches provided by Microsoft, which address specific input validation gaps in affected components. Developers should implement strict allow-listing for input types and enforce rigorous schema validation before processing any external data. Utilizing parameterized queries and avoiding direct concatenation of user inputs into commands or object structures is essential. Additionally, deploying Web Application Firewalls can provide an additional layer of defense by inspecting incoming traffic for known attack patterns associated with improper input handling. Regular security audits and static code analysis tools should be employed to identify similar validation weaknesses in custom applications built on the .NET platform, ensuring that future development practices adhere to secure coding standards such as those outlined in OWASP guidelines.