CVE-2026-81528: CWE-943: Improper Neutralization of Special Elements in Data Query Logic in MongoDB C# Driver
Description
CVE-2026-81528 is a medium severity vulnerability in the MongoDB C# Driver version 2.9.0. The issue arises because the document-replacement code path does not validate element names or shapes as strictly as other write paths, allowing untrusted, loosely-typed input to be interpreted as update logic rather than data. This can lead to unintended execution of database commands under the application's credentials. Applications using strongly-typed document mappings are not affected.
CVSS v4.0
Score 5.3medium
Affected software
MongoDB
C# Driver
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The MongoDB C# Driver version 2.9.0 contains a vulnerability where the document-replacement code path omits validation of element names and shapes that other write paths enforce. As a result, replacement values supplied by an application are forwarded to the database server without neutralizing special query-language elements. If an application passes untrusted, loosely-typed input as a replacement value, this input can be interpreted as update logic by the database, potentially allowing execution of commands with the application's database privileges. Strongly-typed document mappings prevent this issue.
Potential Impact
An attacker able to supply untrusted, loosely-typed input as a replacement document in the affected driver version can cause the database to interpret input as update logic rather than data. This could lead to unintended database command execution under the application's own database credentials. Applications using strongly-typed document mappings are not impacted. There are no known exploits in the wild.
Mitigation Recommendations
No official patch or remediation level has been published yet. Users should avoid passing untrusted, loosely-typed input as replacement values in the MongoDB C# Driver version 2.9.0. Using strongly-typed document mappings mitigates the vulnerability. Monitor vendor advisories for updates and patches.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mongodb
- Date Reserved
- 2026-08-26T22:14:24.585Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a909cffacd9273b49b2d388
Added to database: 08/27/2026, 20:24:31 UTC
Last enriched: 09/10/2026, 03:53:18 UTC
Last updated: 10/10/2026, 18:48:23 UTC
Views: 62
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