CVE-2026-81528: MongoDB C# Driver

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

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 products

• MongoDB C# Driver: from 2.10.0, before 3.11.1 (fixed in 3.11.1)

Published 2026-08-27. Last modified 2026-09-29.