MongoDB C Driver OOB Write in BSONJSON Binary Conversion
CVE-2026-84969 Published on September 3, 2026
Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output
A memory-handling error in the BSON-to-JSON conversion helpers of the MongoDB C Driver can write a small number of bytes past the end of a heap buffer when a binary field is encoded and the output is cut short at a caller-configured length limit. A party who supplies the document content, with no privileges on the application that links the driver, may cause a small amount of data outside the intended buffer to be altered.
Vulnerability Analysis
CVE-2026-84969 can be exploited with network 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
What is a Memory Corruption Vulnerability?
The software writes data past the end, or before the beginning, of the intended buffer. Typically, this can result in corruption of data, a crash, or code execution. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent write operation then produces undefined or unexpected results.
CVE-2026-84969 has been classified to as a Memory Corruption vulnerability or weakness.
Products Associated with CVE-2026-84969
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Affected Versions
MongoDB C Driver:- Version 1.30.0 and below 1.30.9 is affected.
- Version 2.0.0 and below 2.5.2 is affected.