Vulnerability · Published Sep 3, 2026 · Assigned by mongodb
CVE-2026-84969Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output
Low 3.7
In plain English
A low-severity out-of-bounds write 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 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
A memory-handling error in the BSON-to-JSON conversion helpers of the MongoDB C Driver can write a small number of bytes past the end of a heap buffer when a binary field is encoded and the output is cut short at a caller-configured length limit. A party who supplies the document content, with no privileges on the application that links the driver, may cause a small amount of data outside the intended buffer to be altered.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | mongo-c-driver | 1.30.14-r0 | ALPINE-CVE-2026-84969 |
| Debian:13 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-84969 |
| Debian:14 | mongo-c-driver | 2.5.2-1 | DEBIAN-CVE-2026-84969 |
| Ubuntu:26.04:LTS | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-84969 |
| Ubuntu:26.10 | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-84969 |
Affected products (as reported)
Weakness: CWE-787 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N