---
id: "CVE-2026-114650"
kind: "vulnerability"
aliases: ["CVE-2026-114650"]
title: "MongoDB .NET/C# driver: client-side encryption can silently store plaintext fields"
severity: "medium"
cvss: 6.9
epss: 0.00108
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["client-side-encryption", "csharp", "dotnet", "mongodb", "package"]
not_affected_if: ["no-client-side-encryption", "not-using-dotnet-driver"]
published_at: "2026-10-22T19:17:38+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T03:38:52+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-114650", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-114650", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# MongoDB .NET/C# driver: client-side encryption can silently store plaintext fields

Under certain platform text-encoding settings, the MongoDB .NET/C# driver's client-side field-level encryption fails to match an operation to its encryption rules and proceeds without error. Sensitive fields can then be written to MongoDB in plaintext.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed driver version in the project's package references (`MongoDB.Driver` in the .csproj or `packages.lock.json`)
- Check whether the application enables client-side field-level encryption (look for `AutoEncryptionOptions` or `ClientEncryption` in the code)
- unknown for whether a specific platform text-encoding configuration triggers the flaw

## Fix

- Upgrade `MongoDB.Driver` to the patched version listed in the NVD entry (unknown in the sources)
- Verify stored sensitive fields are encrypted after upgrading, by inspecting raw documents in the database

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-114650
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-114650

## From the sources

A flaw in the client-side encryption support of the MongoDB .NET/C# driver can cause data designated for client-side field-level encryption to be written without encryption. Under certain platform text-encoding configurations, an internal name conversion loses information, so the encryption layer fails to associate the operation with its configured encryption rules and the operation proceeds without an error being raised. An application user with the ability to write data through an affected application can therefore have sensitive fields persisted in plaintext, defeating the confidentiality guarantee that client-side encryption is intended to provide. No integrity or availability impact was observed.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_