# CVE-2021-34203: Hardcoded credentials in n/a

> Attackers can exploit hardcoded credentials in the Quagga process to gain telnet access, modify routing, and monitor traffic on D-Link DIR-2640-US routers.

- **Severity:** High 8.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jun 2021
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-gr4j-7v97-rrfc

## What is CVE-2021-34203?

CVE-2021-34203 is a high-severity vulnerability in n/a, published on 16 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

D-Link DIR-2640-US 1.01B04 is vulnerable to Incorrect Access Control. Router ac2600 (dir-2640-us), when setting PPPoE, will start quagga process in the way of whole network monitoring, and this function uses the original default password and port. An attacker can easily use telnet to log in, modify routing information, monitor the traffic of all devices under the router, hijack DNS and phishing attacks. In addition, this interface is likely to be questioned by customers as a backdoor, because the interface should not be exposed.

Weakness: CWE-1188 (Initialization of a Resource with an Insecure Default)

## Which versions are affected by CVE-2021-34203?

It affects 1 product.


Products: Dlink Dir-2640-Us Firmware.

## How do I fix CVE-2021-34203?

No fix has been published for CVE-2021-34203 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34203 being exploited?

There is no known exploitation of CVE-2021-34203 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-20132](https://insights.sbomify.com/CVE-2021-20132/): Hardcoded credentials in Quagga Services on D-Link DIR-2640 Routers (high 8.8)
- [CVE-2021-20134](https://insights.sbomify.com/CVE-2021-20134/): Path traversal in Quagga Services on D-Link DIR-2640 Routers (high 8.4)
- [CVE-2021-34202](https://insights.sbomify.com/CVE-2021-34202/): Memory corruption in n/a (high 7.8)
- [CVE-2021-34201](https://insights.sbomify.com/CVE-2021-34201/): Memory corruption in n/a (high 7.1)
- [CVE-2021-34204](https://insights.sbomify.com/CVE-2021-34204/): Hardcoded credentials in n/a (medium 6.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34203 and fix it if it is affected.

What it is: CVE-2021-34203 is a high-severity vulnerability in n/a, published on 16 Jun 2021. 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-2021-34203 in the wild and no public exploit code.

Affected product: n/a. 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-2021-34203/ (Markdown: https://insights.sbomify.com/CVE-2021-34203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34203
- OSV: https://osv.dev/vulnerability/CVE-2021-34203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34203/
Summaries are generated and may contain mistakes; the official description above is the record.