# CVE-2021-21913: Hardcoded credentials in D-Link

> Hardcoded credentials in the MQTT service allow attackers to execute commands and disclose information on D-Link DIR-3040 routers.

- **Severity:** Critical 10.0 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Sep 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-22wh-wq8h-xvf8

## What is CVE-2021-21913?

CVE-2021-21913 is a critical vulnerability in D-Link, published on 23 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An information disclosure vulnerability exists in the WiFi Smart Mesh functionality of D-LINK DIR-3040 1.13B03. A specially-crafted network request can lead to command execution. An attacker can connect to the MQTT service to trigger this vulnerability.

Weakness: CWE-798 (Use of Hard-coded Credentials)

## Which versions are affected by CVE-2021-21913?

It affects 1 product.


Products: Dlink Dir-3040 Firmware.

## How do I fix CVE-2021-21913?

No fix has been published for CVE-2021-21913 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21913 being exploited?

There is no known exploitation of CVE-2021-21913 in the wild and no public exploit code.

## Other vulnerabilities in D-Link

- [CVE-2021-21820](https://insights.sbomify.com/CVE-2021-21820/): Hardcoded credentials in D-Link (critical 10.0)
- [CVE-2022-44832](https://insights.sbomify.com/CVE-2022-44832/): Command injection in n/a (critical 9.8)
- [CVE-2021-21819](https://insights.sbomify.com/CVE-2021-21819/): Command injection in D-Link (critical 9.1)
- [CVE-2023-41229](https://insights.sbomify.com/CVE-2023-41229/): D-Link DIR-3040 HTTP Request Processing Referer Heap-Based Buffer Overflow Remote Code Execution Vulnerability (high 8.8)
- [CVE-2022-43648](https://insights.sbomify.com/CVE-2022-43648/): Memory corruption in DIR-3040 (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21913 and fix it if it is affected.

What it is: CVE-2021-21913 is a critical vulnerability in D-Link, published on 23 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-21913 in the wild and no public exploit code.

Affected product: D-Link. 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-2021-21913/ (Markdown: https://insights.sbomify.com/CVE-2021-21913/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21913
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21913
- OSV: https://osv.dev/vulnerability/CVE-2021-21913

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21913/
Summaries are generated and may contain mistakes; the official description above is the record.