---
id: "CVE-2026-114654"
kind: "vulnerability"
aliases: ["CVE-2026-114654"]
title: "MongoDB C# Driver: out-of-range BSON binary subtype bypasses integrity checks"
severity: "medium"
cvss: 6.9
epss: 0.00349
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bson", "csharp", "dotnet", "mongodb", "package"]
not_affected_if: ["no-untrusted-text-to-bson-binary"]
published_at: "2026-10-22T19:17:39+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T03:38:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-114654", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-114654", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# MongoDB C# Driver: out-of-range BSON binary subtype bypasses integrity checks

A numeric conversion flaw in the BSON library of the MongoDB C# Driver lets a crafted binary subtype value from text input skip integrity checks. Encoding then writes malformed binary elements that readers reject or misread as shorter than the validated data.

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

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-114654
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-114654

## From the sources

A numeric-type conversion flaw in the BSON handling library of the MongoDB C# Driver allows an out-of-range binary subtype value supplied through untrusted textual input to bypass the library's binary-element integrity checks. When such a value is later encoded, it is narrowed to a smaller wire representation, producing binary elements that misdeclare their type or length. An unauthenticated party able to supply text parsed by an affected application can cause it to emit and persist malformed binary data, which subsequent readers either reject with an error or silently interpret as shorter than the data that was validated.

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