CVE-2026-96749

Heap out-of-bounds write via signed size overflow in BSON document encoding

Published Sep 24, 2026 CVSS 4.0 · 7.5 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-v4x9-3549-crwv PyMongo: PYTHON-5996 Heap out-of-bounds write via signed size overflow in BSON document encoding
History
Type Values Removed Values Added
First Time appeared Mongodb
Mongodb python Driver
Vendors & Products Mongodb
Mongodb python Driver
Type Values Removed Values Added
References
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Heap out-of-bounds write via signed size overflow in BSON document encoding
Weaknesses CWE-190
References
Metrics cvssV3_1

{'score': 8.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 7.5, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mongodb
Published
Updated
Sep 26, 2026, 3:55 AM
Reserved
Sep 23, 2026, 3:45 PM
Status
Awaiting Analysis
Published
Sep 24, 2026, 7:17 PM
Modified
Sep 26, 2026, 4:17 AM
Severity
Important
Public date
Sep 24, 2026, 6:18 PM