# CVE-2026-6231: bson_validate may skip validation when processing certain inputs

> The MongoDB C Driver may incorrectly validate BSON data, allowing malformed inputs to bypass checks and potentially cause downstream processing errors.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Apr 2026
- **Updated:** 13 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-6231, GHSA-q869-m422-4qcv, JLSEC-2026-773, UBUNTU-CVE-2026-6231

## What is CVE-2026-6231?

CVE-2026-6231 is a medium-severity vulnerability in MongoDB Inc. C Driver, published on 13 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The bson_validate function may return early on specific inputs and incorrectly report success. This behavior could result in skipping validation for BSON data, allowing malformed or invalid UTF-8 sequences to bypass validation and be processed incorrectly. The issue may affect applications that rely on these functions to validate untrusted BSON data before further processing. This issue affects MongoDB C Driver versions prior to 1.30.5, MongoDB C Driver version 2.0.0 and MongoDB C Driver version 2.0.1

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-6231?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-6231?

Upgrade to a fixed version.

## Is CVE-2026-6231 being exploited?

There is no known exploitation of CVE-2026-6231 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB Inc. C Driver

- [CVE-2026-93393](https://insights.sbomify.com/CVE-2026-93393/): Heap overflow via oversized decrypted TLS record sequence in Windows Secure Channel stream (critical 9.2)
- [CVE-2026-6691](https://insights.sbomify.com/CVE-2026-6691/): MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow (high 8.6)
- [CVE-2026-84964](https://insights.sbomify.com/CVE-2026-84964/): Heap corruption via OCSP request double free from crafted multi-URL certificate in TLS client (high 8.2)
- [CVE-2024-7553](https://insights.sbomify.com/CVE-2024-7553/): Accessing Untrusted Directory May Allow Local Privilege Escalation (high 7.3)
- [CVE-2026-93395](https://insights.sbomify.com/CVE-2026-93395/): Integer Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer() (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-6231 and fix it if it is affected.

What it is: CVE-2026-6231 is a medium-severity vulnerability in MongoDB Inc. C Driver, published on 13 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-6231 in the wild and no public exploit code.

Affected product: MongoDB Inc. C Driver. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-6231/ (Markdown: https://insights.sbomify.com/CVE-2026-6231/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6231
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6231
- OSV: https://osv.dev/vulnerability/CVE-2026-6231

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-6231/
Summaries are generated and may contain mistakes; the official description above is the record.