CVE-2026-96229 in .NET
Summary
by MITRE • 10/14/2026
Permissive list of allowed inputs in .NET allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves a permissive configuration or implementation within the Microsoft .NET framework that fails to adequately restrict the set of allowable input values for specific operations. This lack of strict validation creates a condition where an external, unauthenticated actor can interact with system components in ways not intended by the developer. The core technical flaw lies in the absence of rigorous input filtering and type checking mechanisms when processing data received from networked sources. Instead of enforcing a whitelist approach that limits inputs to known safe values, the application accepts a broad range of characters or parameters, which allows an attacker to craft malicious payloads designed to exploit parsing logic errors or misinterpretations within the underlying runtime environment.
This architectural weakness directly facilitates information disclosure attacks by enabling unauthorized access to sensitive data stored on the server or accessible through system calls triggered by these malformed inputs. An attacker can leverage this flaw to extract internal configuration details, stack traces, database connection strings, or other proprietary logic that should remain hidden from external users. The operational impact is significant as it compromises the confidentiality of the application and its underlying infrastructure. By exposing such information, attackers gain valuable intelligence that can be used for further exploitation, including privilege escalation, lateral movement within a network, or targeted attacks against specific services identified in the leaked data.
From a classification perspective, this issue aligns with CWE-20 Improper Input Validation, as the system fails to verify that user-supplied input conforms to expected formats and constraints before processing it. It also relates closely to CWE-787 Out-of-bounds Write if the permissive inputs lead to buffer overflows or memory corruption during parsing, although in this specific context of information disclosure, it is more accurately categorized under CWE-209 Generation of Error Message Containing Sensitive Information when the result is visible error output. In terms of offensive security frameworks, this vulnerability supports techniques found in MITRE ATT&CK such as T1504 Weak or Compromised Authentication Credentials if authentication bypasses are involved, but more directly it facilitates reconnaissance activities like T1213 Data from Information Repositories where the attacker queries internal systems to gather intelligence.
To mitigate this risk, developers must implement strict input validation strategies that adhere to a deny-by-default philosophy. This involves defining explicit allowlists for all acceptable inputs based on type, length, range, and format rather than relying on negative filtering which can be easily bypassed using encoding tricks or edge cases. Utilizing parameterized queries and ORM frameworks where applicable helps prevent injection-based data leakage. Additionally, error handling mechanisms should be configured to return generic messages to end-users while logging detailed diagnostic information securely for internal review only. Regular security code reviews focused on input processing logic and automated static analysis tools can help identify these permissive configurations before deployment into production environments.