CVE-2026-93759 in Mongoid
Summary
by MITRE • 09/18/2026
Mongoid does not neutralize a string-typed query criterion supplied to its query builder, and instead passes it to the database as a server-side JavaScript expression. An unauthenticated party able to influence the value an application supplies as a query argument may cause code of their choosing to be evaluated by the database engine. This may result in unintended disclosure of stored field values, unintended selection of documents for application-initiated writes, and reduced database performance.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified involves a critical server-side JavaScript injection flaw within Mongoid, an Object-Document Mapper (ODM) for Ruby applications interacting with MongoDB databases. The core technical deficiency lies in the query builder's failure to properly sanitize or neutralize string-typed query criteria before they are transmitted to the database engine. Instead of treating these inputs as literal data values intended for comparison or filtering, Mongoid passes them directly into a context where the database interprets them as executable JavaScript code. This architectural oversight transforms standard query parameters into potential vectors for arbitrary code execution on the server side, fundamentally breaking the separation between application logic and database interpretation layers.
From an operational perspective, this flaw allows any unauthenticated party or attacker who can influence the input values of a Mongoid query to inject malicious JavaScript expressions. When these injected strings are processed by MongoDB, they are evaluated as part of the query execution pipeline. This capability leads to severe security consequences beyond simple data leakage. An attacker can craft payloads that cause unintended disclosure of stored field values across documents that should remain inaccessible due to access control policies. Furthermore, because the injection occurs at the database level during query evaluation, it may allow for the unintended selection of specific documents intended for application-initiated write operations, potentially leading to unauthorized data modification or deletion without triggering standard application-level validation checks.
The impact extends beyond immediate confidentiality and integrity breaches to include significant availability concerns through reduced database performance. Maliciously crafted JavaScript expressions can be designed to consume excessive computational resources during evaluation, effectively creating a denial-of-service condition against the MongoDB instance. This resource exhaustion affects not only the targeted collection but potentially the entire database server depending on configuration and load balancing strategies. The ability to manipulate query results also undermines data consistency, as applications relying on accurate filtering for business logic may process incorrect datasets, leading to cascading errors in downstream systems that depend on this application layer.
This vulnerability aligns with CWE-94, commonly known as Improper Control of Generation of Code (Code Injection), specifically where user input is directly executed by a server-side engine without adequate sanitization. In the context of the MITRE ATT&CK framework, this behavior corresponds to techniques involving Server-Side Request Forgery or direct code injection via database query manipulation, often categorized under T1059 if it leads to further command execution on underlying infrastructure through stored procedures or aggregation pipelines that support JavaScript. The attack vector is typically classified as Network-based with low complexity for exploitation if the vulnerable endpoint is exposed, though authentication requirements may vary based on specific deployment configurations and network segmentation.
Mitigation strategies must prioritize immediate patching of Mongoid to versions where this input validation issue has been resolved by enforcing strict type checking and escaping mechanisms before query construction. Developers should avoid passing raw user-supplied strings directly into query criteria unless those values are strictly validated against expected formats such as ObjectId, integer, or boolean types. Implementing parameterized queries that explicitly define data types can prevent the database engine from interpreting input as executable code. Additionally, applying principle of least privilege to database accounts ensures that even if injection occurs, the scope of potential damage is limited by restricting permissions for write operations and administrative functions on affected collections. Regular security audits focusing on dynamic query construction patterns are essential to identify similar vulnerabilities in other parts of the application stack.