CVE-2026-84966: An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cau

Routine

MEDIUM 5.1UPGRADE

CVE-2026-84966 is a medium-severity flaw (CVSS 5.1) affecting c\+\+ driver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cause a length value to be interpreted incorrectly. When an application supplies an extremely large, non-terminated field name to the builder, the library may read memory outside the intended buffer and terminate the calling process. No authentication is required, but the calling application must pass the oversized name in a specific form.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.1 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 96%)
CISA exploited list	No
Weakness	CWE-681
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 15:54 UTCUpdated Record last modified

mongodb c\+\+ driver UPGRADE

Affected: >= 3.0.0 and < 4.5.2

Fixed in: 4.5.2

Safe to downgrade to: a release before 3.0.0

1. Check installed version

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

2. UPGRADE to 4.5.2 (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 3.0.0 (Debian / Ubuntu)

apt-cache madison c++-driver sudo apt install c++-driver=<VERSION_BEFORE_3.0.0> 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_3.0.0> 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-2026-84966?

c\+\+ driver: upgrade to 4.5.2. Exact commands for each OS are on this page.

Is CVE-2026-84966 being exploited?

CVE-2026-84966 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-2026-84966 affect?

CVE-2026-84966 affects c\+\+ driver. Severity is medium (CVSS 5.1). An incorrect numeric type conversion in the BSON document building component of the MongoDB C++ Driver may cause a length value to be interpreted incorrectly. When an application supplies an extremely large, non-terminated field name to the

How urgent is CVE-2026-84966?

Priority 19/100. No elevated risk signals yet.

Software pages

MongoDB vulnerabilities

Related CVEs

CVE-2026-81522 HIGH 8.1 UPGRADE A weakness in the MongoDB C++ Driver's handling of caller-supplied namespace identifiers allows special charac
CVE-2026-88034 HIGH 8.3 UPGRADE Improper neutralization of special elements in data query logic in the GridFS component of the MongoDB C++ Dri
CVE-2026-84970 MEDIUM 6.2 UPGRADE A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library

References

← Back to latest CVEs