# CVE-2026-81528: NoSQL injection via array replacement bypassing update shape validation in driver write path

> CVE-2026-81528: NoSQL injection via array replacement bypassing update shape validation in driver write path. CVSS 5.4 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-81528
Last updated: 2026-09-29T19:16:27Z

- Published: 2026-08-27 18:32 UTC · Updated: 2026-09-29 19:16 UTC · Assigner: mongodb
- CVSS: 5.4 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
- EPSS: 0.28%, 20th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-943

## Description

A MongoDB C\# driver document-replacement code path omits the element-name/shape validation that the equivalent write paths apply, so a value supplied as a replacement is forwarded to the server without neutralization of query-language special elements. An application that passes untrusted, loosely-typed input as a replacement value therefore allows that input to be interpreted by the database as update logic rather than as data, executing under the application's own database credentials. Applications using strongly-typed document mappings are not affected.

## 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-2026-81528)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-81528)
- [https://jira.mongodb.org/browse/CSHARP-6158](https://jira.mongodb.org/browse/CSHARP-6158)
- [https://www.nuget.org/packages/MongoDB.Driver/3.11.1](https://www.nuget.org/packages/MongoDB.Driver/3.11.1)

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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-2026-81528 · Markdown: https://rewindex.com/cve/CVE-2026-81528.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-81528 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:25.031Z