# CVE-2026-18691: Improper Authentication in MongoDB Intra-Cluster Connections Allows Credential Exposure

> CVE-2026-18691: Improper Authentication in MongoDB Intra-Cluster Connections Allows Credential Exposure. CVSS 8.8 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-18691
Last updated: 2026-10-23T21:10:00Z

- Published: 2026-08-11 18:46 UTC · Updated: 2026-10-23 21:10 UTC · Assigner: mongodb
- CVSS: 8.8 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS: 0.36%, 29th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-757

## Description

An issue in MongoDB Server's intra-cluster connection setup could allow a party with suitable network access to influence which authentication mechanism is used when one replica set member connects to another. Under certain conditions, this could cause the cluster's shared internal credential to be transmitted in a less-protected form, potentially allowing that credential to be recovered. If recovered, the credential could be used to authenticate as the internal superuser to nodes in the deployment.

## Affected vendors and products

- MongoDB: MongoDB Server

## Tracked companies

- [MongoDB Atlas](https://rewindex.com/company/mongodb-atlas.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-18691)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-18691)
- [https://jira.mongodb.org/browse/SERVER-130264](https://jira.mongodb.org/browse/SERVER-130264)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-18691 · Markdown: https://rewindex.com/cve/CVE-2026-18691.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-18691 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:17:08.794Z