# CVE-2026-106437: mongo-c-driver: The BSON buffer-reservation API in the MongoDB C Driver can record a length smaller than the five-byte BSON minimum

CVE-2026-106437 is fixed in mongo-c-driver on 1 platform by DEBIAN-CVE-2026-106437 (version 2.5.6-1), released October 16, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-106437
- Priority: High
- CVSS: 7.4 (high)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 8, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | mongo-c-driver Debian 14 | 2.5.6-1 | [DEBIAN-CVE-2026-106437](https://patchblox.com/security/data/fix/linux/debian-cve-2026-106437.md) | Oct 16, 2026 |

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Data as of 2026-11-09T19:38:12Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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