Vulnerability · Published Sep 3, 2026 · Assigned by mongodb
CVE-2026-84963Silent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parser
Medium 5.3
In plain English
A medium-severity security flaw in C Driver from MongoDB. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
An incorrect numeric conversion in the JSON parsing component of the MongoDB C Driver's BSON library may cause an unusually large text value to be silently shortened, or the corresponding field to be omitted, while the parsing operation still reports success and returns no error. An unauthenticated party who can supply the input processed by an application that uses this component may cause that application to hold data that does not match what was submitted, which may result in unintended alteration of data.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | mongo-c-driver | 1.30.14-r0 | ALPINE-CVE-2026-84963 |
| Debian:12 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-84963 |
| Debian:13 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-84963 |
| Debian:14 | mongo-c-driver | 2.5.2-1 | DEBIAN-CVE-2026-84963 |
| Ubuntu:26.04:LTS | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-84963 |
| Ubuntu:26.10 | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-84963 |
Affected products (as reported)
Weakness: CWE-681 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N