What is CVE-2026-106431?

CVE-2026-106431 is a medium-severity vulnerability in MongoDB C Driver, classified under Out-of-bounds Write. CVSS score: 5.7/10. Published 2026-10-08.

How severe is CVE-2026-106431?

Medium severity. CVSS v3 base score is 5.7 out of 10.

Buffer overflow in MongoDB C Driver

CVE-2026-106431

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.

Vulnerability class: Buffer Overflow

Published 2026-10-08 · last modified 2026-10-08.

CVSS v3 metric

CVSS v3 base score 5.7 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

MongoDB C Driver

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

jira.mongodb.org/browse/CDRIVER-6418

Frequently asked questions

What is CVE-2026-106431?: CVE-2026-106431 is a medium-severity vulnerability in MongoDB C Driver, classified under Out-of-bounds Write. CVSS score: 5.7/10. Published 2026-10-08.
How severe is CVE-2026-106431?: Medium severity. CVSS v3 base score is 5.7 out of 10.