CVE-2026-120567 in Entity Framework Core Provider
Summary
by MITRE • 11/03/2026
The MongoDB Entity Framework Core provider does not neutralize special elements when it places a caller-supplied value into a bulk update that is expressed as a databasea result, a value supplied as plain data may be interpreted by the database as expression syntax. A part value through normal application input may causeunintended modification of fields in the records the application is updating, and may cause data already held in those records to be relocated into other fields of the same record.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability described involves a critical injection flaw within the MongoDB Entity Framework Core provider, specifically affecting how bulk update operations are processed when they result in database-level expressions rather than simple value assignments. This issue stems from a failure to properly sanitize or neutralize special elements contained within caller-supplied values before these values are incorporated into the query structure sent to the MongoDB server. In standard application logic, user input is typically treated as literal data; however, due to this implementation defect, certain inputs can be interpreted by the database engine as executable expression syntax rather than static content. This misinterpretation occurs because the provider does not adequately escape or encode characters that hold special meaning within MongoDB's query language, allowing an attacker to inject code-like structures into fields intended for plain data storage.
From a technical perspective, this flaw represents a form of NoSQL injection where the application layer fails to enforce strict type separation between data and logic during bulk operations. When a developer utilizes the Entity Framework Core provider to perform updates, the framework constructs MongoDB commands based on the provided objects. If these objects contain properties with values that include specific delimiters or operators recognized by MongoDB's expression parser, those characters are passed through without transformation. Consequently, what appears as harmless text input in the application interface is translated into complex query expressions at the database level. This behavior violates the principle of least privilege and proper data validation, allowing external inputs to alter the semantic meaning of the update command itself rather than just its parameters.
The operational impact of this vulnerability is severe, leading directly to unauthorized modification of record fields and potential data integrity compromise. An attacker can exploit this flaw by supplying crafted input that causes unintended modifications to existing records beyond the scope of the intended application logic. Specifically, the injection allows for the relocation of data already held within a document into different fields of the same record. This means sensitive information stored in one field could be inadvertently overwritten or moved, disrupting the logical structure of the database documents. Such manipulation can lead to significant business logic errors, as applications relying on specific field locations may fail or behave unpredictably when their expected data structures are altered by malicious input.
This vulnerability aligns with CWE-94, which covers Improper Control of Generation of Code (Code Injection), and more specifically relates to injection flaws in NoSQL databases where user input influences the structure of the query rather than just its parameters. In terms of offensive security frameworks, this behavior is consistent with ATT&CK technique T1190, Exploit Public-Facing Application, as it leverages a flaw in how an application processes external inputs to execute unintended commands within the backend database system. The ability to manipulate field locations and trigger side effects through bulk updates highlights a critical gap in input validation strategies commonly found in ORM-based integrations with document stores.
To mitigate this risk, developers must ensure that all user-supplied data is strictly validated and sanitized before being passed to the Entity Framework Core provider for bulk operations. Implementing allow-lists for expected character sets can prevent special symbols from entering the system entirely. Additionally, upgrading to patched versions of the MongoDB EF Core provider where such injection vectors have been addressed by properly escaping or parameterizing inputs is essential. Application-level controls should also be reinforced to treat all incoming data as opaque strings unless explicitly defined otherwise, ensuring that no part of user input can influence the structural syntax of database commands. Regular security audits focusing on ORM configurations and query construction patterns are recommended to identify similar vulnerabilities in other parts of the application stack.