CVE-2026-84966

An out-of-bounds write in the connection-monitoring logic of the MongoDB C Driver may allow an unauthenticated party controlling name resolution and host responses to write beyond a heap buffer, potentially causing the application to terminate unexpectedly.

A heap-based buffer overflow exists in the TLS transport layer of the MongoDB C Driver when built with the Windows platform TLS backend. A remote endpoint that the client connects to can cause the driver to write uncontrolled data outside the bounds of a heap allocation while processing incoming encrypted traffic after the TLS handshake completes. No authentication or user interaction is required, because the affected processing occurs before any application-level authentication completes. Triggering this issue may lead to memory corruption in the client process, disclosure of adjacent heap memory, or termination of the process.

Improper neutralization of special elements in data query logic in the GridFS component of the MongoDB C Driver causes a caller-supplied structured file identifier to be interpreted as a query condition rather than a literal identifier. An authenticated user who can influence the identifier may obtain stored file content beyond the intended target or cause all GridFS file chunks in the affected bucket to be removed.

A size check in the client-side authentication path of the MongoDB C Driver can wrap around, so an unusually large user-name value is accepted and copied past the end of a small buffer. A party able to set the driver's connection settings may cause the application that embeds the driver to terminate unexpectedly. Reaching this code requires a build in which the optional external SASL authentication backend is present and a connection configured to use it.

Improper neutralization of special elements in data query logic in the GridFS component of the MongoDB C++ Driver causes a caller-supplied structured file identifier to be interpreted as a query condition rather than a literal identifier. An authenticated user who can influence the identifier may obtain stored file content beyond the intended target or cause all GridFS file chunks in the affected bucket to be removed.

The MongoDB C# Driver contains improper neutralization of regular-expression metacharacters in the LINQ query translation component. A caller-supplied character sequence can alter a regular-expression predicate generated by an affected application.

Improper neutralization of special elements in data query logic in the GridFS component of the MongoDB C# Driver can cause a caller-supplied structured file identifier to be interpreted as a query condition rather than as a literal identifier. An authenticated user who can influence the identifier passed by an affected application may obtain stored file content beyond the intended target, cause all GridFS file chunks in the affected bucket to be removed, or rename a stored file other than the intended target.

A double free in the OpenSSL-based TLS certificate revocation checking path of the MongoDB C Driver can be triggered by specially crafted certificate data during the handshake, causing the same heap object to be released twice and leading to unexpected termination of the client application.

An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause an unusually large text value to be silently shortened or the corresponding field to be omitted, while the parsing operation still reports success and returns no error.

A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library. An actor who controls the text that an embedding application hands to the library's public JSON parsing interface, when that text is very large, can cause the library to read memory beyond the supplied buffer and return it to the caller, to silently accept only part of the input as a complete document, or to terminate the process. No MongoDB server, credentials, or non-default configuration is required; the effect is confined to the process that uses the library.