CVE-2026-18703

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MongoDB Server Certificate Authentication Bypass

Publication date: 2026-08-11

Last updated on: 2026-08-28

Assigner: MongoDB, Inc.

Description

An issue in MongoDB Server could allow a party with a valid client certificate and a corresponding user account to authenticate using a certificate-based authentication method, even when an administrator has configured the server to restrict authentication to other mechanisms. This could allow authentication through a method the administrator intended to disable.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-11

Last Modified

2026-08-28

Generated

2026-09-01

AI Q&A

2026-08-12

EPSS Evaluated

2026-08-30

NVD

CVE-2026-18703

EUVD

EUVD-2026-56861

Affected Vendors & Products

Vendor	Product	Version / Range
mongodb	mongodb_server	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-863	The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Attack-Flow Graph

Executive Summary

This vulnerability in MongoDB Server allows a user with a valid client certificate and account to authenticate even when certificate-based authentication is disabled by an administrator. The administrator may have intended to restrict authentication to other methods, but this flaw permits bypassing that restriction.

Detection Guidance

To detect this vulnerability, check MongoDB server logs for certificate-based authentication attempts. Look for successful authentications despite configured restrictions. Verify server configuration files for misconfigured auth mechanisms. Use commands like 'mongod --version' to check MongoDB version and 'grep -r "certificate" /etc/mongod.conf' to inspect configuration.

Impact Analysis

If exploited, this could allow unauthorized access to the MongoDB server despite administrator restrictions. Attackers with a valid certificate could gain access to sensitive data, potentially leading to data breaches or unauthorized modifications.

Compliance Impact

This vulnerability could lead to unauthorized access to personal or sensitive data, violating compliance requirements such as GDPR or HIPAA. Organizations may face legal penalties, reputational damage, and loss of trust due to data breaches resulting from this flaw.

Mitigation Strategies

Review MongoDB server configuration to ensure certificate-based authentication is properly restricted. Disable any unintended authentication methods and verify user account permissions. Update to the latest MongoDB version if available.

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