CVE-2026-93763 in Mongoid
Summary
by MITRE • 09/18/2026
A protection mechanism failure in the object-document mapper's encryption configuration generation can cause fields that an application declared for client-side field-level encryption to be written and kept in cleartext, without any error or warning. A party holding ordinary read access to the database can then read values that were intended to be protected from that party. This may result in unintended disclosure of sensitive information.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/18/2026
The vulnerability described represents a critical failure in the implementation of client-side field-level encryption within an object-document mapper, specifically during the generation or application of its configuration settings. In modern database-driven applications, particularly those utilizing NoSQL databases like MongoDB, it is common practice to encrypt sensitive fields such as personally identifiable information (PII), financial data, or health records at the application layer before persistence. This approach ensures that even if an attacker gains read access to the underlying storage medium or compromises a low-privilege database account, they cannot decipher the protected values without possessing the corresponding encryption keys and algorithms configured in the application logic. The flaw lies in the mechanism responsible for translating developer-declared encryption intents into actual cryptographic operations during data serialization. When this protection mechanism fails silently, it results in plaintext fields being written to the database alongside encrypted ones, creating a significant inconsistency in security posture that is difficult to detect through standard monitoring tools because no error codes or warnings are generated by the framework itself.
From a technical perspective, this issue aligns with CWE-327, which categorizes the use of a broken or risky cryptographic algorithm as a weakness, but more specifically it reflects CWE-916 regarding improper control of encryption key usage for authentication and data integrity. The core defect is not necessarily in the strength of the underlying cipher suite, such as AES-GCM or ChaCha20-Poly1305, which are typically robust when implemented correctly. Instead, the vulnerability stems from a logic error where the mapper fails to apply the encryption transformation to specific fields that were explicitly marked for protection by the application developer. This could be due to misconfigured schema definitions, race conditions during configuration loading, or bugs in the serialization pipeline that bypasses the encryption interceptor under certain edge cases. Because the failure is silent, developers may operate under the false assumption that their sensitive data is secure, leading to a complete breakdown of the confidentiality guarantee provided by client-side encryption architectures.
The operational impact of this vulnerability is severe and directly compromises the principle of least privilege regarding database access rights. In many enterprise environments, application service accounts are granted read-only or limited write permissions to specific collections within the database to mitigate the blast radius in case of a compromise. If an attacker exploits other vulnerabilities, such as SQL injection (though less common in NoSQL) or simply gains legitimate credentials through phishing or credential stuffing attacks, they can query these databases directly using standard tools like mongo shell or GUI clients. Under normal circumstances, encrypted fields would appear as unreadable ciphertext strings. However, due to this configuration generation failure, the attacker will encounter plaintext values indistinguishable from other non-sensitive data fields. This allows for the mass exfiltration of sensitive information without triggering alerts associated with anomalous decryption attempts or unauthorized key usage, thereby facilitating identity theft, financial fraud, and regulatory violations under frameworks such as GDPR, HIPAA, or PCI-DSS.
This scenario maps directly to several techniques within the MITRE ATT&CK framework, particularly T1078 Valid Accounts, where an attacker uses legitimate credentials to access resources they are not authorized to view. Furthermore, it relates to T1539 Steal Web Application Session Cookies if session data is stored in plaintext fields, or more broadly to Data Exfiltration over Unencrypted Network Connection (T1041) when the stolen data is transmitted out of the network. The silent nature of the failure also complicates incident response and forensic analysis, as standard database audit logs will show successful read operations on seemingly normal data, masking the fact that confidential information was accessed in violation of policy. Detection relies heavily on application-level logging rather than infrastructure monitoring, requiring developers to implement custom checks or periodic integrity scans to verify that encryption is being applied consistently across all designated fields.
Mitigation strategies must address both immediate remediation and long-term architectural resilience. The primary fix involves patching the object-document mapper to ensure that its configuration generation logic correctly identifies and applies encryption transformations to all fields declared in the schema for client-side protection. Developers should implement rigorous unit tests that specifically verify the output of serialization processes, ensuring that encrypted fields are never persisted as plaintext. Additionally, integrating static application security testing (SAST) tools configured with rulesets that detect potential misconfigurations in cryptographic libraries can help identify such issues during the development phase rather than at runtime. For existing deployments, a comprehensive audit of database contents is necessary to identify any records where sensitive data was stored in cleartext due to this flaw. These records must be re-encrypted using valid keys and secure algorithms immediately.
To prevent recurrence, organizations should adopt a defense-in-depth strategy that does not rely solely on application-layer encryption for confidentiality guarantees against insider threats or compromised service accounts. Database-level encryption (TDE) provides an additional layer of protection at rest, ensuring that even if the application fails to encrypt specific fields, the underlying storage remains protected unless the database master key is also compromised. Furthermore, implementing strict access controls and monitoring via SIEM solutions can help detect unusual patterns in data access, such as bulk reads from collections containing sensitive information. Regular penetration testing focused on authentication bypasses and privilege escalation should include checks for this type of configuration drift to ensure that security mechanisms remain effective throughout the application lifecycle.