MongoDB Python Driver up to 4.18.1 BSON Document Encoding integer overflow

Summaryinfo

A vulnerability described as very critical has been identified in MongoDB Python Driver up to 4.18.1. This affects an unknown function of the component BSON Document Encoding. Such manipulation leads to integer overflow. This vulnerability is documented as CVE-2026-96749. The attack needs to be performed locally. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in MongoDB Python Driver up to 4.18.1. Affected by this issue is an unknown code block of the component BSON Document Encoding. The manipulation with an unknown input leads to a integer overflow vulnerability. Using CWE to declare the problem leads to CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-96749 since 09/23/2026. The exploitation is known to be easy. The attack needs to be approached locally. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/24/2026).

Upgrading to version 4.18.2 eliminates this vulnerability.

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Productinfo

Type

• Database Software

Vendor

• MongoDB

Name

• Python Driver

Version

• 4.18.0
• 4.18.1

License

• open-source

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