CVE-2026-81529: MongoDB C# Driver

High severity, CVSS 7.1. EPSS: 0.3% chance of exploitation in the next 30 days.

Improper neutralization of delimiters in connection-URL construction allows connection-option injection in the MongoDB C# Driver. When an application passes untrusted text into the driver's connection-URL builder and round-trips the builder back into a client configuration, the untrusted text is serialized without neutralizing the URL/option delimiters and is then re-parsed as authoritative connection options. A low-privileged user of such an application can thereby introduce or suppress security-relevant connection settings.

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.