Vulnerability · Published Oct 8, 2026 · Assigned by mongodb
CVE-2026-106437Out-of-bounds read and write via undersized BSON buffer reservation in MongoDB C Driver
Medium 6.2
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 0.1% (higher than 3% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
The BSON buffer-reservation API in the MongoDB C Driver can record a length smaller than the five-byte BSON minimum. Later append or comparison operations can underflow unsigned length calculations and read or write outside the document buffer. An actor who can influence the length supplied by an embedding application can cause the application to terminate or read or corrupt adjacent process memory. Reaching this issue requires the application to pass an undersized value to bson_reserve_buffer and then perform an affected operation.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-106437 |
| Debian:13 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-106437 |
| Debian:14 | mongo-c-driver | 2.5.6-1 | DEBIAN-CVE-2026-106437 |
| Ubuntu:26.04:LTS | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-106437 |
| Ubuntu:26.10 | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-106437 |
Affected products (as reported)
Weakness: CWE-191 · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H