# CVE-2026-114647: MongoDB C# Driver NoSQL injection in FindOneAndReplace

Source: https://junglewise.ai/threats/cve-2026-114647-the-mongodb-c-driver-does-not-reject-replacement-documents-whose  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-22. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

CVE-2026-114647 · Severity: medium · CVSS 4.3 · Published 2026-10-22

The MongoDB C# Driver contains a vulnerability in its FindOneAndReplace method that allows attackers to inject update operators when they control field names in the replacement document. Instead of replacing the document entirely, the server executes attacker-supplied operators like $set or $unset, silently modifying the database in ways the application did not intend. Applications that accept user-supplied field names when constructing replacement documents are vulnerable to data corruption and unauthorized field manipulation.

Technologies: [MongoDB C Driver](https://junglewise.ai/threats/technologies/c-driver). Vendors: [MongoDB](https://junglewise.ai/threats/vendors/mongodb).

## Quick answers

**Is CVE-2026-114647 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-114647 being exploited in the wild.

**How severe is CVE-2026-114647?** Medium severity, with a CVSS score of 4.3, published 22 October 2026.

**Which products and versions are affected?** MongoDB C Driver 2.13.0 through 3.12.x.

**Is there a fix for CVE-2026-114647?** Yes: fixed in 3.13.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-114647 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-114647?** Check whether you run MongoDB C Driver at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 3.13.0

## Technical details

The FindOneAndReplace operation fails to validate that top-level field names in the replacement document do not start with a dollar sign, unlike other replace operations in the driver. When a replacement document's first element name begins with '$', the server interprets it as an update operator command rather than a document to store. The vulnerability exists because GetCommandValidator returns NoOpElementNameValidator.Instance instead of applying ReplacementElementNameValidator, leaving the replacement unvalidated at the wire protocol level.

## Affected products

- MongoDB C# Driver 2.13.0 through 3.12.x

## Timeline

- 2026-10-22: disclosed
- 2026-10-22: patched: MongoDB C# Driver 3.13.0 released

## References

- [https://github.com/mongodb/mongo-csharp-driver/releases/tag/v3.13.0](https://github.com/mongodb/mongo-csharp-driver/releases/tag/v3.13.0)
- [https://jira.mongodb.org/browse/CSHARP-6186](https://jira.mongodb.org/browse/CSHARP-6186)

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