Vulnerability · Published Oct 8, 2026 · Assigned by mongodb
CVE-2026-106431One-byte heap buffer overflow in BSON bulk document writer in MongoDB C Driver
Medium 5.7
In plain English
A medium-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 0.1% (higher than 1% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
An off-by-one error in the BSON bulk document writer in the MongoDB C Driver can write one zero byte immediately past a heap allocation when a document ends at a specific buffer boundary. An actor who can influence the size of documents serialized by an embedding application can corrupt adjacent process memory or terminate the process. Reaching this issue requires the application to use the BSON bulk-writer API and produce a precise cumulative document size.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-106431 |
| Debian:13 | mongo-c-driver | no fix listed | DEBIAN-CVE-2026-106431 |
| Debian:14 | mongo-c-driver | 2.5.6-1 | DEBIAN-CVE-2026-106431 |
| Ubuntu:26.04:LTS | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-106431 |
| Ubuntu:26.10 | mongo-c-driver | no fix listed | UBUNTU-CVE-2026-106431 |
Affected products (as reported)
Weakness: CWE-787 · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H