CVE-2026-81527

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NoSQL Injection in MongoDB C# Driver

Publication date: 2026-08-27

Last updated on: 2026-08-28

Assigner: MongoDB, Inc.

Description

A NoSQL/expression injection weakness exists in the LINQ-to-aggregation query translation layer of the MongoDB C# Driver, in both aggregation expression and query filter translation. When application-supplied values are embedded in certain query constructs, special elements contained within those values are not properly escaped before the resulting query is transmitted to the database, so portions of the value may be interpreted by the database as query logic rather than as data. A user able to supply values that an application incorporates into an affected query may thereby cause unintended data to be returned or query results to be altered.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-27

Last Modified

2026-08-28

Generated

2026-09-17

AI Q&A

2026-08-28

EPSS Evaluated

2026-09-15

NVD

CVE-2026-81527

Affected Vendors & Products

Vendor	Product	Version / Range
mongodb	mongodb_csharp_driver	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-943	The product generates a query intended to access or manipulate data in a data store such as a database, but it does not neutralize or incorrectly neutralizes special elements that can modify the intended logic of the query.

Attack-Flow Graph

Executive Summary

This vulnerability is a NoSQL or expression injection weakness in the LINQ-to-aggregation query translation layer of the MongoDB C# Driver. When application-supplied values are embedded in certain query constructs, special elements within those values are not properly escaped before the query is sent to the database. This allows parts of the value to be interpreted as query logic instead of data, potentially altering query results or returning unintended data.

Detection Guidance

This vulnerability involves NoSQL/expression injection in the MongoDB C# Driver's LINQ-to-aggregation query translation layer. Detection requires reviewing application code for unsafe query construction patterns where user input is embedded without proper sanitization. Check for use of LINQ expressions in aggregation pipelines or filters that incorporate untrusted input.

Impact Analysis

An attacker could exploit this to manipulate queries, causing the application to return incorrect or sensitive data. This may lead to unauthorized access to information, data leaks, or application behavior changes without proper authorization.

Compliance Impact

This vulnerability could lead to unauthorized data access or leaks, violating confidentiality requirements in GDPR and HIPAA. Compliance may be compromised if sensitive data is exposed, potentially resulting in legal penalties or reputational damage.

Mitigation Strategies

Update the MongoDB C# Driver to the latest version that patches this vulnerability. Review application code to ensure user-supplied values are properly escaped or validated before being embedded in queries. Implement input validation and use parameterized queries where possible.

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