# CVE-2026-84970: Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser

> CVE-2026-84970: Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser. CVSS 6.2 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-84970
Last updated: 2026-09-10T19:47:31Z

- Published: 2026-09-03 14:56 UTC · Updated: 2026-09-10 19:47 UTC · Assigner: mongodb
- CVSS: 6.2 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
- EPSS: 0.12%, 2th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-681

## Description

A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library. An actor who controls the text that an embedding application hands to the library's public JSON parsing interface, when that text is very large, can cause the library to read memory beyond the supplied buffer and return it to the caller, to silently accept only part of the input as a complete document, or to terminate the process. No MongoDB server, credentials, or non-default configuration is required; the effect is confined to the process that uses the library.

## Affected vendors and products

- MongoDB: 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-2026-84970)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-84970)
- [https://jira.mongodb.org/browse/CXX-3547](https://jira.mongodb.org/browse/CXX-3547)

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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-2026-84970 · Markdown: https://rewindex.com/cve/CVE-2026-84970.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-84970 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:46.485Z