---
id: CVE-2026-93394
title: >-
  A flaw in libmongoc's SCRAM authentication implementation caused the client to
  continue the authentication handshake and transmit the client proof even when
  a nonce mismatch was detected in the server's first message
summary: >-
  A flaw in libmongoc's SCRAM authentication implementation caused the client to
  continue the authentication handshake and transmit the client proof even when
  a nonce mismatch was detected in the server's first message. An unauthorized
  par…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-303
vendor: MongoDB Inc.
product: C Driver
affected:
  - c_driver >= 2.0.0 < 2.3.2
published: '2026-09-17'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T19:05:01.127'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93394'
references:
  - url: 'https://jira.mongodb.org/browse/CDRIVER-6315'
    label: cna@mongodb.com
tags:
  - nvd
  - cve.org
epss: 0.00321
epssPercentile: 0.2245
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-18T14:27:52.100964Z'
ingestedAt: '2026-09-17T21:29:16.992Z'
---

## Overview

A flaw in libmongoc's SCRAM authentication implementation caused the client to continue the authentication handshake and transmit the client proof even when a nonce mismatch was detected in the server's first message. An unauthorized party with a man-in-the-middle position could exploit this by injecting a crafted server-first-message containing a controlled salt and low iteration count, then capturing the resulting client proof to perform offline password cracking. This vulnerability is mitigated by TLS, which is standard in production deployments.

## Remediation

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