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CVE-2026-96749

PyMongo: PYTHON-5996 Heap out-of-bounds write via signed size overflow in BSON document encoding

Published Oct 5, 2026 · updated Oct 15, 2026

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.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 5, 2026 · GitHub Advisory Database

    Detected

    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 wit

  2. Oct 6, 2026 · GitHub Advisory Database

    Fix available

    pymongo fixed in 4.18.2

  3. Oct 6, 2026 · GitHub Advisory Database

    Fix available

    pymongo fixed in 4.18.2

  4. Oct 6, 2026 · GitHub Advisory Database

    Updated

    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 wit

  5. Oct 15, 2026 · GitHub Advisory Database

    Updated

    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 wit

Affected

  • PyPI pymongo0 → 4.18.2

Sources

  • GitHub Advisory DatabasePackage advisoryGHSA-v4x9-3549-crwv

    GitHub Advisory Database record mirrored by OSV.

    github.com
  • OSV.devPackage advisoryGHSA-v4x9-3549-crwv

    PyMongo: PYTHON-5996 Heap out-of-bounds write via signed size overflow in BSON document encoding

    osv.dev

References