CVE-2026-96749
PyMongo: PYTHON-5996 Heap out-of-bounds write via signed size overflow in BSON document encoding
Published Oct 5, 2026 · corrected/updated Oct 15, 2026 · evidence confidence high
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.
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-96749 is a high public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: pymongo (0 → 4.18.2). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 8.4. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-190. Sources contributing to this record: cve_org, github, osv. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
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
Oct 6, 2026 · GitHub Advisory Database
Fix available
pymongo fixed in 4.18.2
Oct 6, 2026 · GitHub Advisory Database
Fix available
pymongo fixed in 4.18.2
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
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
- CVE.orgVulnerability recordCVE-2026-96749
Official CVE identifier
cve.org - 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