CVE-2026-106431: MongoDB C Driver

Medium severity, CVSS 5.7. EPSS: 0.1% chance of exploitation in the next 30 days.

An off-by-one error in the BSON bulk document writer in the MongoDB C Driver can write one zero byte immediately past a heap allocation when a document ends at a specific buffer boundary. An actor who can influence the size of documents serialized by an embedding application can corrupt adjacent process memory or terminate the process. Reaching this issue requires the application to use the BSON bulk-writer API and produce a precise cumulative document size.

Affected products

• MongoDB C Driver: from 0.5.0, before 1.30.13 (fixed in 1.30.13); from 2.0.0, before 2.5.6 (fixed in 2.5.6)

Published 2026-10-08. Last modified 2026-10-08.