CVE-2026-84965: An integer wraparound in an allocation size calculation in the BSON library's JSON parsing code can cause a bu

Routine

MEDIUM 5.1UPGRADE

CVE-2026-84965 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 integer wraparound in an allocation size calculation in the BSON library's JSON parsing code can cause a buffer to be released while a following copy operation still writes through the stale pointer. On builds where sizes are 32 bits, an unauthenticated party able to supply a sufficiently large JSON input to an application that links the library may cause that application to terminate unexpectedly, resulting in denial of service.

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 98%)
CISA exploited list	No
Weakness	CWE-190
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 16:00 UTCUpdated Record last modified

mongodb c driver UPGRADE

Affected: >= 1.10.0 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 1.10.0

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 1.10.0 (Debian / Ubuntu)

apt-cache madison c-driver sudo apt install c-driver=<VERSION_BEFORE_1.10.0> 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_1.10.0> 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-2026-84965?

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

Is CVE-2026-84965 being exploited?

CVE-2026-84965 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-2026-84965 affect?

CVE-2026-84965 affects c driver. Severity is medium (CVSS 5.1). An integer wraparound in an allocation size calculation in the BSON library's JSON parsing code can cause a buffer to be released while a following copy operation still writes through the stale pointer. On builds where sizes are 32 bits, an

How urgent is CVE-2026-84965?

Priority 18/100. No elevated risk signals yet.

Software pages

MongoDB vulnerabilities

Related CVEs

CVE-2026-6231 MEDIUM 4.3 UPGRADE The bson_validate function may return early on specific inputs and incorrectly report success
CVE-2026-6691 HIGH 7.8 UPGRADE The MongoDB C Driver's Cyrus SASL integration performs unsafe string copying during username canonicalization,
CVE-2026-81524 MEDIUM 5.4 UPGRADE A weakness in the MongoDB C Driver allows special elements in caller-supplied database and collection name com
CVE-2026-84963 MEDIUM 5.3 UPGRADE An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause
CVE-2026-84964 MEDIUM 5.9 UPGRADE A double free in the OpenSSL-based TLS certificate revocation checking path of the MongoDB C Driver can be rea

References

← Back to latest CVEs