CVE-2026-84964: MongoDB C Driver

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

A double free in the OpenSSL-based TLS certificate revocation checking path of the MongoDB C Driver can be reached by a TLS endpoint that the client already trusts. During the handshake, specially formed certificate data can cause the same heap object to be released twice. An unauthenticated party acting as the trusted endpoint may cause the connecting client application to terminate unexpectedly.

Affected products

• MongoDB C Driver: from 1.17.0, before 1.30.9 (fixed in 1.30.9); from 2.0.0, before 2.5.2 (fixed in 2.5.2)

Published 2026-09-03. Last modified 2026-09-22.