CVE-2026-96749: MongoDB Python Driver

High severity, CVSS 8.4. EPSS: 0.1% chance of exploitation in the next 30 days.

An integer overflow in the BSON document encoding component of the MongoDB Python Driver's bundled native extension may occur when a single document is built from an unusually large amount of caller-supplied data. Size arithmetic is performed in a signed 32-bit type, and the guard meant to catch the overflow is written in a form whose behavior is not defined by the C language standard. A party with no privileges who can place a very large value into data that an application encodes may, depending on how the native extension was built, cause a write outside the bounds of an allocated buffer inside the application's own process.

Affected products

• MongoDB Python Driver: from 1.9.0, before 4.18.2 (fixed in 4.18.2)

Published 2026-09-24. Last modified 2026-09-26.