# CVE-2026-93394: libmongoc SCRAM client nonce-validation bypass

> CVE-2026-93394: libmongoc SCRAM client nonce-validation bypass. CVSS 3.7 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-93394
Last updated: 2026-09-25T20:33:17Z

- Published: 2026-09-17 20:31 UTC · Updated: 2026-09-25 20:33 UTC · Assigner: mongodb
- CVSS: 3.7 (CVSS 3.1) · Severity: Low · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- EPSS: 0.32%, 25th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-303

## Description

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.

## Affected vendors and products

- MongoDB Inc.: C Driver

## Tracked companies

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

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-93394)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-93394)
- [https://jira.mongodb.org/browse/CDRIVER-6315](https://jira.mongodb.org/browse/CDRIVER-6315)

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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-2026-93394 · Markdown: https://rewindex.com/cve/CVE-2026-93394.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-93394 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:22.232Z