CVE-2026-88035: MongoDB C Driver

Medium severity, CVSS 5.5. EPSS: 0.1% chance of exploitation in the next 30 days.

A size check in the client-side authentication path of the MongoDB C Driver can wrap around, so an unusually large user-name value is accepted and copied past the end of a small buffer. A party able to set the driver's connection settings may cause the application that embeds the driver to terminate unexpectedly. Reaching this code requires a build in which the optional external SASL authentication backend is present and a connection configured to use it.

Affected products

• MongoDB C Driver: from 1.10.0, before 1.30.10 (fixed in 1.30.10); from 2.2.0, before 2.5.3 (fixed in 2.5.3)

Published 2026-09-10. Last modified 2026-09-16.