# CVE-2026-84963: Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser

> CVE-2026-84963: Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser. CVSS 5.3 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-84963
Last updated: 2026-09-22T16:22:04Z

- Published: 2026-09-03 15:03 UTC · Updated: 2026-09-22 16:22 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:L/A:N
- EPSS: 0.31%, 24th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-681

## Description

An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause an unusually large text value to be silently shortened, or the corresponding field to be omitted, while the parsing operation still reports success and returns no error. An unauthenticated party who can supply the input processed by an application that uses this component may cause that application to hold data that does not match what was submitted, which may result in unintended alteration of data.

## 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-2026-84963)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-84963)
- [https://jira.mongodb.org/browse/CDRIVER-6407](https://jira.mongodb.org/browse/CDRIVER-6407)

---

_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-2026-84963 · Markdown: https://rewindex.com/cve/CVE-2026-84963.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-84963 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T04:04:37.137Z