CVE-2026-96749: Heap out-of-bounds write via signed size overflow in BSON document encoding
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.
Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H · CWE-190
Tracked companies
Mapped from the CVE’s affected-product data, NVD CPE matches, vendor advisories or package feeds. A mapping means the vendor’s software is named, not that its hosted service was exposed.
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
MongoDB: Python Driver
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- github.com/mongodb/mongo-python-driver/blob/4.18.2/doc/changelog.rst (opens in new tab)
- github.com/mongodb/mongo-python-driver/releases/tag/4.18.2 (opens in new tab)
- github.com/mongodb/mongo-python-driver/security/advisories/GHSA-v4x9-3549-crwv (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)