Bug 2531592 (CVE-2026-88035)

Summary: CVE-2026-88035 mongodb-c-driver: MongoDB C Driver: Denial of Service via heap buffer overflow in SASL authentication
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the MongoDB C Driver. This vulnerability, a heap buffer overflow, occurs in the client-side authentication process when handling unusually large usernames. An attacker who can control the driver's connection settings could exploit this to cause the application using the driver to crash, leading to a denial of service. Exploitation requires the optional external SASL (Simple Authentication and Security Layer) authentication backend to be enabled and configured.
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Description OSIDB Bzimport 2026-09-10 18:32:02 UTC 
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.