---
id: CVE-2026-81527
title: >-
  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
summary: >-
  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
  certa…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-943
vendor: mongodb
product: c#_driver
affected:
  - 'c#_driver >= 2.10.0, < 3.11.1'
patched:
  - c#_driver 3.11.1
published: '2026-08-27'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T19:16:34.617'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81527'
references:
  - url: 'https://jira.mongodb.org/browse/CSHARP-6156'
    label: cna@mongodb.com
  - url: 'https://www.nuget.org/packages/MongoDB.Driver/3.11.1'
    label: cna@mongodb.com
tags:
  - nvd
epss: 0.00306
epssPercentile: 0.2102
ingestedAt: '2026-09-29T19:44:04.117Z'
---

## Overview

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.

## Affected

- `c#_driver >= 2.10.0, < 3.11.1`

## Remediation

Upgrade past the affected range:

- `c#_driver 3.11.1`