MongoDB C++ Driver: BSON Length Conv Bug Causing Crash
CVE-2026-84966 Published on September 3, 2026
BSON element injection via NUL-embedded document keys in builder append
An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cause a length value to be interpreted incorrectly. When an application supplies an extremely large, non-terminated field name to the builder, the library may read memory outside the intended buffer and terminate the calling process. No authentication is required, but the calling application must pass the oversized name in a specific form.
Vulnerability Analysis
CVE-2026-84966 is exploitable with local system access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
Incorrect Conversion between Numeric Types
When converting from one data type to another, such as long to integer, data can be omitted or translated in a way that produces unexpected values. If the resulting values are used in a sensitive context, then dangerous behaviors may occur.
Products Associated with CVE-2026-84966
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Affected Versions
MongoDB C++ Driver:- Version 3.2.0 and below 4.5.2 is affected.