CVE-2026-96749 HIGH

CVE-2026-96749: Heap out-of-bounds write via signed size overflow in BSON document encoding

Vendor Mongodb
Product Python Driver
Weakness CWE-190
Published September 24, 2026
Last update September 26, 2026

CVSS base score

7.5/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

September 24, 2026 CVE published
September 26, 2026 Record updated