CVE-2021-20331: MongoDB C# Driver may publish events containing authentication-related data to a command listener configured by an application

Severity: medium (CVSS 4.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-13 · updated 2026-06-17
Weakness: CWE-200

Description

Specific versions of the MongoDB C# Driver may erroneously publish events containing authentication-related data to a command listener configured by an application. The published events may contain security-sensitive data when commands such as "saslStart", "saslContinue", "isMaster", "createUser", and "updateUser" are executed. Without due care, an application may inadvertently expose this authenticated-related information, e.g., by writing it to a log file. This issue only arises if an application enables the command listener feature (this is not enabled by default). This issue affects the MongoDB C# Driver v2.12 versions prior to and including 2.12.1.

Affected products

MongoDB Inc MongoDB .NET/C# Driver: from 2.12.0 before 2.12.2; 2.11.0 — fixed in 2.12.2

How to fix

Upgrade to a fixed version: MongoDB Inc MongoDB .NET/C# Driver 2.12.2. Check the vendor advisory for mitigations.

References

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