Double Free in MongoDB C Driver

CVE-2026-84964

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.

Vulnerability class: Double Free

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.003 (16.2th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-84964: held from 0.001 to 0.003.

EPSS over last 30 days · oldest: 0.001 · newest: 0.003 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-84964?
CVE-2026-84964 is a medium-severity vulnerability in MongoDB C Driver, classified under Double Free. CVSS score: 5.9/10. Published 2026-09-03.
How severe is CVE-2026-84964?
Medium severity. CVSS v3 base score is 5.9 out of 10.