CVE-2026-84965 Heap write primitive via size round-up wrap during JSON parsing on 32-bit builds
An integer overflow in the MongoDB C Driver's JSON parser on 32-bit systems allows unauthenticated attackers to cause a denial of service via large inputs.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-84965?
CVE-2026-84965 is a medium-severity vulnerability in MongoDB C Driver, published on 3 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-190
Which versions are affected by CVE-2026-84965?
It affects 1 product.
Products include Mongodb C Driver.
How do I fix CVE-2026-84965?
Upgrade to a fixed version.
Is CVE-2026-84965 being exploited?
There is no known exploitation of CVE-2026-84965 in the wild and no public exploit code.
Other vulnerabilities in MongoDB C Driver
- CVE-2026-93393 Heap overflow via oversized decrypted TLS record sequence in Windows Secure Channel stream
- CVE-2026-6691 MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow
- CVE-2026-84964 Heap corruption via OCSP request double free from crafted multi-URL certificate in TLS client
- CVE-2024-7553 Accessing Untrusted Directory May Allow Local Privilege Escalation
- CVE-2026-93395 Integer Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer()
Sources
Also known as DEBIAN-CVE-2026-84965, UBUNTU-CVE-2026-84965.