# CVE-2026-93395: Integer Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer()

> CVE-2026-93395: Integer Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer(). CVSS 5.3 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-93395
Last updated: 2026-09-25T20:32:52Z

- Published: 2026-09-17 20:34 UTC · Updated: 2026-09-25 20:32 UTC · Assigner: mongodb
- CVSS: 5.3 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- EPSS: 0.40%, 34th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-191

## Description

A missing lower-bound validation in the bson\_new\_from\_buffer() function of libbson allows an integer underflow when processing BSON data with a zero-length prefix. The function reads a 32-bit document length from the input buffer but does not verify that the value is at least 5 (the minimum valid BSON document size) before using it in an array index calculation. When the length field is zero, the expression used to check the document's null terminator wraps to UINT32\_MAX, causing a heap out-of-bounds read that crashes the process. An unauthorized party who can supply crafted BSON input to an application using this API can cause a denial of service.

## 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-2026-93395)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-93395)
- [https://jira.mongodb.org/browse/CDRIVER-6343](https://jira.mongodb.org/browse/CDRIVER-6343)

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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-2026-93395 · Markdown: https://rewindex.com/cve/CVE-2026-93395.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-93395 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:14:25.951Z