CVE-2026-81520

When mongosqld is configured with a client certificate authority file, the listener requests a client certificate during the TLS handshake but does not require one, so a client that presents no certificate is still accepted. In deployments that rely on client certificates as the sole means of identifying users, a remote party with network access to the listener can therefore establish a session and read the MongoDB data exposed through the connector.

An unauthenticated party able to reach the port of a MongoDB Connector for BI (mongosqld) instance may generate enough routine connection log activity to exhaust the storage backing the configured log path. When a log write or log rotation operation subsequently fails, the resulting error is not handled and the shared mongosqld process ends, ending service for all connected SQL clients. The process continues to end on startup until an operator restores available storage, and the diagnostic message explaining the condition is not recorded.

A database user able to create a view in a namespace that MongoDB Connector for BI samples can cause the schema-sampling routine to stop functioning by defining a view whose evaluation reliably fails. The sampling logic classifies the resulting server message as transient and, after the configured retries are exhausted, proceeds without a valid result, ending the schema refresh routine. The mongosqld process continues running without a usable schema, so SQL clients are unable to obtain results until an operator removes the view or excludes its namespace from sampling.

In MongoDB Connector for BI, MongoDB object names such as collection, field, and index names are placed into the quoted identifiers of the DDL text returned by SHOW CREATE statements without escaping the identifier delimiter. A user with permission to write to a sampled MongoDB collection can choose a name that closes the quoted identifier early, so that additional SQL text becomes part of the generated output. If an operator or automated tool later replays that generated statement against a SQL server, the additional text is executed with the privileges of that session.

In MongoDB Connector for BI, the description text of a collection's JSON schema validator is incorporated into the comment text of the DDL returned by SHOW CREATE statements without complete escaping of backslash characters. A user with permission to modify a collection's schema validator, in deployments configured to build their SQL schema from those validators, can cause additional SQL text to be embedded in that generated output. If an operator or automated tool later replays that generated statement against a SQL server, the additional text is executed with the privileges of that session.

In MongoDB Connector for BI, mongodrdl may write a TLS private-key password to standard error when the password is supplied through both the connection URI and the corresponding command-line option. A local user with access to the captured output can use the password to access the TLS client key.

An unauthenticated client that can reach a MongoDB Connector for BI deployment configured with Kerberos authentication may cause mongosqld to terminate when a crafted authentication exchange encounters a specific GSSAPI error-handling condition. This can interrupt BI Connector availability until the process restarts.