CVE-2026-84964: A double free in the OpenSSL-based TLS certificate revocation checking path of the MongoDB C Driver can be rea

Routine

MEDIUM 5.9REMOTEWATCHLISTUPGRADE

CVE-2026-84964 is a medium-severity flaw (CVSS 5.9) affecting c driver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 83%)
CISA exploited list	No
Weakness	CWE-415
Published	2026-09-03
Last modified	2026-09-22

Publisher (CNA): MongoDB, Inc. · Vendor: mongodb

Last updated 2026-09-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-03 16:18 UTCPublished CVE record published
2026-09-22 16:19 UTCUpdated Record last modified

mongodb c driver UPGRADE

Affected: >= 1.17.0 and < 1.30.9 · >= 2.0.0 and < 2.5.2

Fixed in: 1.30.9, 2.5.2

Safe to downgrade to: a release before 1.17.0

1. Check installed version

apt-cache policy c-driver || rpm -q c-driver || c-driver --version

2. UPGRADE to 1.30.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade c-driver

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade c-driver

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.17.0 (Debian / Ubuntu)

apt-cache madison c-driver sudo apt install c-driver=<VERSION_BEFORE_1.17.0> sudo apt-mark hold c-driver

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list c-driver sudo dnf downgrade c-driver-<VERSION_BEFORE_1.17.0> sudo dnf versionlock add c-driver

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-84964?

c driver: upgrade to 1.30.9, 2.5.2. Exact commands for each OS are on this page.

Is CVE-2026-84964 being exploited?

CVE-2026-84964 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-84964 affect?

CVE-2026-84964 affects c driver. Severity is medium (CVSS 5.9). 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

How urgent is CVE-2026-84964?

Priority 35/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSL vulnerabilities · MongoDB vulnerabilities

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References

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