CVE-2026-84964
Double-free in MongoDB C Driver TLS handshake can crash client apps.
Is CVE-2026-84964 being exploited?
Not confirmed. CVE-2026-84964 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.26% probability of exploitation in the next 30 days.
How severe is CVE-2026-84964?
CVE-2026-84964 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-84964?
Yes. A fix has been recorded for CVE-2026-84964. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-84964 affect?
CVE-2026-84964 affects MongoDB C Driver (libmongoc), Applications linking libmongoc, Clients using OpenSSL revocation path. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-84964?
Update libmongoc to vendor-patched release when available; restrict/trust TLS endpoints.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
An unauthenticated trusted TLS endpoint can send crafted certs that trigger a double-free during handshake, causing client process crash (DoS) and possible memory corruption.
Patch when possible
- affected>= 1.17.0 and < 1.30.9
- affected>= 2.0.0 and < 2.5.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.