CVE-2026-81530 in C# Driver
Summary
by MITRE • 08/27/2026
A weakness in the client-side encryption configuration surface of the MongoDB C# Driver causes sensitive key-management credential material supplied by the application to be reproduced verbatim in the driver's human-readable diagnostic representation of its client settings, instead of being masked as other secret fields are. A party able to read the application's logs, diagnostic output, or a process memory dump may thereby recover the plaintext credentials and use them to decrypt protected field data.
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Analysis
by VulDB Data Team • 08/27/2026
The MongoDB C# Driver contains a configuration weakness in its client-side encryption implementation that results in the improper handling of sensitive key-management credential material. Specifically, when an application supplies these credentials for configuring encrypted fields or automatic decryption capabilities, the driver fails to mask this specific information within its human-readable diagnostic representations of client settings. While other secret fields such as connection strings are appropriately obscured with placeholder characters like asterisks or dots in log outputs and debug dumps, the encryption keys remain exposed in plaintext. This inconsistency indicates a gap in the sanitization logic applied during the serialization of configuration objects for logging purposes, allowing sensitive cryptographic material to be written directly into diagnostic streams without obfuscation.
This vulnerability creates a significant risk for organizations relying on MongoDB client-side field-level encryption to protect data at rest or in transit. The primary operational impact stems from the exposure of plaintext credentials through standard application artifacts. Attackers who gain access to server logs, console output, debug traces, or even process memory dumps can extract these unmasked keys. Once obtained, these credentials allow an adversary to decrypt protected field data that was previously secured by MongoDB's encryption mechanisms. This effectively nullifies the security controls intended to safeguard sensitive information such as personally identifiable information, financial records, or health data stored within encrypted database fields. The exposure is particularly dangerous because log files are often retained for extended periods and may be accessible to a wide range of personnel or third-party monitoring tools that do not have strict access controls equivalent to those protecting the actual database content.
From a classification perspective, this issue aligns with CWE-532, which covers information exposure through log files, as well as CWE-798, concerning the use of hardcoded credentials, although in this case, the credential is dynamically supplied but improperly handled rather than statically embedded. The vulnerability also relates to CWE-209, where an error condition generates information that could assist an attacker in exploiting a product. In terms of offensive security frameworks, this flaw facilitates data exfiltration and undermines confidentiality controls, mapping broadly to techniques associated with unauthorized access to sensitive information via log analysis or memory scraping within the MITRE ATT&CK framework's collection phase. The failure to mask secrets is a common oversight in software development that can lead to severe compliance violations under regulations such as GDPR, HIPAA, or PCI-DSS, which mandate strict protection of cryptographic keys and personal data.
To mitigate this vulnerability, developers must ensure that all sensitive configuration parameters are consistently masked across all diagnostic outputs generated by the MongoDB C# Driver. This involves updating logging configurations to apply uniform obfuscation rules to encryption-related fields similar to those applied to connection strings and authentication tokens. Application owners should also implement strict access controls on log storage systems to prevent unauthorized viewing of diagnostic data, even if masking is imperfectly implemented. Upgrading to a patched version of the MongoDB C# Driver that addresses this specific logging flaw is critical for restoring proper security postures. Additionally, organizations should conduct regular audits of their application logs and memory dumps using automated secret detection tools to identify any instances where plaintext credentials may have already been exposed prior to applying patches.