CVE-2026-93762 in Mongoid
Summary
by MITRE • 09/18/2026
Mongoid contains an unsafe reflection weakness in the query path used for embedded documents. An application that passes an externally supplied field name to certain in-memory query methods may allow an unauthenticated party to obtain unintended disclosure of stored document data and to permanently remove stored records.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within Mongoid, a popular Object-Document Mapper (ODM) for Ruby applications interacting with MongoDB, represents a critical security flaw rooted in unsafe reflection mechanisms during the query execution phase for embedded documents. This weakness arises when an application developer inadvertently passes user-controlled input directly as field names or keys into specific in-memory query methods without adequate sanitization or validation. In standard software development practices, dynamic method invocation based on external input is a common pattern that requires strict guardrails to prevent unintended side effects. However, the implementation within this particular component of Mongoid fails to sufficiently restrict which fields can be targeted by these queries when dealing with embedded document structures. This lack of restriction allows an attacker who has access to the application interface but lacks authentication credentials to manipulate the internal state of the database through crafted requests that exploit the reflection capabilities inherent in the Ruby language and the ODM's design.
From a technical perspective, this flaw aligns closely with CWE-94, commonly known as Improper Control of Generation of Code or Commands (Code Injection), specifically manifesting here as unsafe reflection where user input dictates method execution paths. The vulnerability is further contextualized by its potential to lead to CWE-200, Exposure of Sensitive Information to an Unauthorized Actor, and CWE-611, Improper Restriction of XML External Entity Reference, although the latter is less direct; more accurately, it falls under CWE-918 due to Server-Side Request Forgery-like behaviors where internal logic is manipulated. The core issue lies in how Mongoid processes query parameters for embedded documents. When an external party supplies a field name that corresponds to sensitive data or administrative functions within the document structure, the ODM executes queries against these fields without verifying if such access should be permitted by the current user context. This bypasses standard authorization checks because the vulnerability operates at the data retrieval and manipulation layer before higher-level business logic can enforce role-based access controls effectively.
The operational impact of this vulnerability is severe, encompassing both confidentiality and integrity compromises for affected systems. An unauthenticated attacker can exploit this flaw to perform unintended disclosure of stored document data. By carefully constructing queries that target specific embedded fields containing sensitive information such as personally identifiable information (PII), financial records, or proprietary business logic, the attacker can extract data that was never intended to be exposed via public APIs. Furthermore, the vulnerability extends beyond read operations; it allows for the permanent removal of stored records. This capability enables an attacker to delete critical data from MongoDB collections associated with embedded documents, leading to significant availability issues and potential loss of historical or transactional integrity. The combination of unauthorized data exfiltration and destructive deletion capabilities makes this a high-severity issue that can disrupt business operations and violate regulatory compliance requirements such as GDPR or HIPAA depending on the nature of the stored data.
In terms of threat modeling, this vulnerability maps to several techniques within the MITRE ATT&CK framework. The initial exploitation phase corresponds to T1059, Command and Scripting Interpreter, specifically through dynamic code execution via reflection. The unauthorized access to sensitive information aligns with T1005, Data from Local System, while the ability to delete records falls under T1485, Data Destruction. Attackers would typically leverage this vulnerability during the initial exploitation phase of an attack chain, often following reconnaissance or phishing efforts that provide them with a foothold in the application layer. The lack of authentication requirement makes it particularly dangerous for internet-facing applications where automated scanning tools can easily discover and exploit such endpoints without needing valid credentials first.
Mitigation strategies must focus on strict input validation and limiting the scope of dynamic method invocations. Developers should avoid passing user-supplied strings directly as field names or keys in query methods unless those values are strictly enumerated against a whitelist of allowed fields. Implementing allowlists for permissible embedded document fields ensures that only predefined, safe attributes can be queried or modified through these interfaces. Additionally, applying principle of least privilege to database connections and ensuring that ODM configurations do not expose internal metadata unnecessarily can reduce the attack surface. Upgrading to patched versions of Mongoid where this reflection weakness has been addressed is essential for immediate remediation. Security teams should also implement Web Application Firewalls (WAFs) with rules tuned to detect anomalous query patterns involving embedded document structures and monitor logs for unusual deletion or read operations on sensitive fields to facilitate rapid incident response if exploitation occurs.