# CVE-2026-84965: Heap write primitive via size round-up wrap during JSON parsing on 32-bit builds

> CVE-2026-84965: Heap write primitive via size round-up wrap during JSON parsing on 32-bit builds. CVSS 5.1 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-84965
Last updated: 2026-09-22T16:00:19Z

- Published: 2026-09-03 15:01 UTC · Updated: 2026-09-22 16:00 UTC · Assigner: mongodb
- CVSS: 5.1 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.12%, 2th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-190

## Description

An integer wraparound in an allocation size calculation in the BSON library's JSON parsing code can cause a buffer to be released while a following copy operation still writes through the stale pointer. On builds where sizes are 32 bits, an unauthenticated party able to supply a sufficiently large JSON input to an application that links the library may cause that application to terminate unexpectedly, resulting in denial of service.

## 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-2026-84965)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-84965)
- [https://jira.mongodb.org/browse/CDRIVER-6405](https://jira.mongodb.org/browse/CDRIVER-6405)

---

_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/)_


---
Canonical: https://rewindex.com/cve/CVE-2026-84965 · Markdown: https://rewindex.com/cve/CVE-2026-84965.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-84965 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:10.529Z