Heap overflow via oversized decrypted TLS record sequence in Windows Secure Channel stream

High8.1CVE-2026-93393 · Published Sep 18, 2026

### Impact 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. ### Patches Fixed in 1.30.11 and 2.5.4. ### Workarounds Ensure server certificate is verified and trusted. ### References https://jira.mongodb.org/browse/CDRIVER-6417