# CVE-2021-20331: MongoDB C# Driver Risk of Exposing Authentication Data via Command Listener

> The MongoDB C# Driver may leak sensitive authentication data to application logs if the command listener feature is enabled.

- **Severity:** Medium 4.2 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 13 May 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-p9rv-qgqw-jx2w

## What is CVE-2021-20331?

CVE-2021-20331 is a medium-severity vulnerability in MongoDB C# Driver, published on 13 May 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Specific versions of the MongoDB C# Driver may erroneously publish events containing authentication-related data to a command listener configured by an application. The published events may contain security-sensitive data when commands such as "saslStart", "saslContinue", "isMaster", "createUser", and "updateUser" are executed. Without due care, an application may inadvertently expose this authenticated-related information, e.g., by writing it to a log file. This issue only arises if an application enables the command listener feature (this is not enabled by default). This issue affects the MongoDB C# Driver v2.12 versions prior to and including 2.12.1.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-20331?

2 open source packages ship an affected version, including mongodb.driver. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mongodb.driver` | NuGet | From 2.11.0 | 2.12.2 |
| `mongodb.driver` | NuGet | From 2.11.0 | 2.12.2 |

Products: Mongodb C\# Driver.

## How do I fix CVE-2021-20331?

Upgrade mongodb.driver to 2.12.2 or later.

## Is CVE-2021-20331 being exploited?

There is no known exploitation of CVE-2021-20331 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB C# Driver

- [CVE-2026-88026](https://insights.sbomify.com/CVE-2026-88026/): Regular expression injection via unescaped characters in LINQ query translation in MongoDB C# Driver (high 7.1)
- [CVE-2026-81529](https://insights.sbomify.com/CVE-2026-81529/): Connection-option injection via unescaped settings in the canonical MongoDB URL builder (high 7.1)
- [CVE-2026-81527](https://insights.sbomify.com/CVE-2026-81527/): NoSQL injection via unquoted constant GroupBy keys in LINQ pipeline translation (medium 6.9)
- [CVE-2026-81530](https://insights.sbomify.com/CVE-2026-81530/): KMS master key exposure via unredacted credential serialization in driver settings string (medium 6.8)
- [CVE-2022-48282](https://insights.sbomify.com/CVE-2022-48282/): Deserializing compromised object with MongoDB .NET/C# Driver may cause remote code execution (medium 6.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20331 and fix it if it is affected.

What it is: CVE-2021-20331 is a medium-severity vulnerability in MongoDB C# Driver, published on 13 May 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-20331 in the wild and no public exploit code.

Affected packages and fixed versions:
- mongodb.driver (NuGet): affected from 2.11.0; fixed in 2.12.2
- mongodb.driver (NuGet): affected from 2.11.0; fixed in 2.12.2

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-2021-20331/ (Markdown: https://insights.sbomify.com/CVE-2021-20331/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20331
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20331
- OSV: https://osv.dev/vulnerability/CVE-2021-20331

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20331/
Summaries are generated and may contain mistakes; the official description above is the record.