# CVE-2026-106438: Silent Decimal128 value corruption via incorrect exactness check in MongoDB C Driver

> Attackers can cause data corruption by providing malformed decimal strings to applications using the MongoDB C Driver, leading to incorrect numeric values being stored.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-106438, UBUNTU-CVE-2026-106438

## What is CVE-2026-106438?

CVE-2026-106438 is a medium-severity vulnerability in MongoDB C Driver, published on 8 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An incorrect calculation in Decimal128 string parsing in the MongoDB C Driver can accept certain over-precision inputs containing leading zeros instead of rejecting them. This produces a value different from the supplied text. An actor who can provide a decimal string to an embedding application, including through Extended JSON parsing, can cause the application to store or use an incorrect numeric value.

Weakness: CWE-682 (Incorrect Calculation)

## Which versions are affected by CVE-2026-106438?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-106438?

Upgrade to a fixed version.

## Is CVE-2026-106438 being exploited?

There is no known exploitation of CVE-2026-106438 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB 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-2026-106438 and fix it if it is affected.

What it is: CVE-2026-106438 is a medium-severity vulnerability in MongoDB C Driver, published on 8 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-106438 in the wild and no public exploit code.

Affected product: MongoDB 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-2026-106438/ (Markdown: https://insights.sbomify.com/CVE-2026-106438/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106438
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106438
- OSV: https://osv.dev/vulnerability/CVE-2026-106438

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-106438/
Summaries are generated and may contain mistakes; the official description above is the record.