CVE-2026-93393 in C Driver
Summary
by MITRE • 09/18/2026
A heap-based buffer overflow exists in the TLS transport layer of the MongoDB C Driver when built with the Windows platform TLS backend. A remote endpoint that the client connects to, or an attacker able to impersonate or redirect the client's connection, can cause the driver to write attacker-supplied data outside the bounds of a heap allocation while processing incoming encrypted traffic. No authentication or user interaction is required, because the affected processing occurs before any application-level authentication completes. Successful exploitation may lead to memory corruption in the client process, disclosure of adjacent heap memory, or termination of the process.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified as a heap-based buffer overflow resides within the TLS transport layer of the MongoDB C Driver when compiled with the Windows platform TLS backend. This specific implementation flaw arises during the processing of incoming encrypted traffic, where the driver fails to adequately validate data boundaries before writing attacker-supplied content into memory buffers allocated on the heap. The root cause is a classic boundary check failure that allows an external entity to overwrite adjacent memory locations beyond the intended allocation limits. Because this processing occurs at the transport layer prior to any application-level authentication or user interaction, the vulnerability can be triggered by simply establishing a connection to a malicious server or through man-in-the-middle attacks where traffic is redirected. This lack of required authentication significantly expands the attack surface, allowing remote attackers to exploit the flaw without needing valid credentials on the MongoDB instance itself.
From an operational perspective, successful exploitation of this heap-based buffer overflow can lead to severe consequences for the client application running the driver. The immediate impact includes memory corruption within the client process, which may result in unpredictable behavior or crashes. Furthermore, because the write operation extends beyond the allocated buffer boundaries, it is possible to read and disclose contents from adjacent heap memory regions that were not intended to be accessed by the current execution context. This side-channel effect can lead to information disclosure of sensitive data stored in nearby memory blocks. In more severe scenarios, precise control over the overwritten memory structures could allow an attacker to execute arbitrary code within the context of the client process, effectively achieving remote code execution. The termination of the process remains a common outcome if the corruption triggers critical security checks or causes segmentation faults during normal operation.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-120, which describes buffer copy without checking size limits, specifically manifesting as a heap-based overflow under CWE-787. The attack vector is classified under MITRE ATT&CK technique T1190, Exploit Public-Facing Application, as it targets an application accessible over the network that handles untrusted input from external sources. Additionally, the potential for reading adjacent memory relates to information disclosure principles often associated with CWE-200 or CWE-416, depending on whether the focus is on the mechanism of access or the result. The absence of authentication requirements places this in a high-severity category within threat modeling frameworks due to its ease of exploitation by any network actor capable of intercepting or initiating connections.
Mitigation strategies for this vulnerability primarily involve updating the MongoDB C Driver to a version that includes patches addressing these buffer boundary checks. Developers should ensure that all dependencies and libraries linked with their applications are kept current, particularly those handling TLS encryption on Windows platforms where specific backend implementations may have unique memory management quirks. In environments where immediate patching is not feasible, network-level controls such as firewalls or intrusion prevention systems can be configured to inspect TLS traffic for anomalies indicative of buffer overflow attempts, although this is less effective against encrypted payloads unless deep packet inspection with decryption capabilities are employed. Application developers should also consider implementing strict input validation and using memory-safe programming practices in custom wrappers around the driver to add additional layers of defense-in-depth against similar classes of vulnerabilities.