---
id: CVE-2026-106437
title: >-
  The BSON buffer-reservation API in the MongoDB C Driver can record a length
  smaller than the five-byte BSON minimum
summary: >-
  The BSON buffer-reservation API in the MongoDB C Driver can record a length
  smaller than the five-byte BSON minimum. Later append or comparison operations
  can underflow unsigned length calculations and read or write outside the
  document …
severity: medium
cvss: 6.2
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H'
cwe:
  - CWE-191
published: '2026-10-08'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T20:49:23.240'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-106437'
references:
  - url: 'https://jira.mongodb.org/browse/CDRIVER-6423'
    label: cna@mongodb.com
tags:
  - nvd
ingestedAt: '2026-10-08T20:06:22.183Z'
---

## Overview

The BSON buffer-reservation API in the MongoDB C Driver can record a length smaller than the five-byte BSON minimum. Later append or comparison operations can underflow unsigned length calculations and read or write outside the document buffer. An actor who can influence the length supplied by an embedding application can cause the application to terminate or read or corrupt adjacent process memory. Reaching this issue requires the application to pass an undersized value to bson_reserve_buffer and then perform an affected operation.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.