# CVE-2021-20134: Path traversal in Quagga Services on D-Link DIR-2640 Routers

> Authenticated attackers can exploit path traversal in Quagga services to overwrite scripts, achieving remote code execution and root access on D-Link DIR-2640 routers.

- **Severity:** High 8.4 (`CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-v4h7-5mx9-q833

## What is CVE-2021-20134?

CVE-2021-20134 is a high-severity path traversal vulnerability in Quagga Services on D-Link DIR-2640 Routers, published on 30 Dec 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 are affected by an absolute path traversal vulnerability that allows a remote, authenticated attacker to set an arbitrary file on the router's filesystem as the log file used by either Quagga service (zebra or ripd). Subsequent log messages will be appended to the file, prefixed by a timestamp and some logging metadata. Remote code execution can be achieved by using this vulnerability to append to a shell script on the router's filesystem, and then awaiting or triggering the execution of that script. A remote, unauthenticated root shell can easily be obtained on the device in this fashion.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2021-20134?

It affects 1 product.


Products: Dlink Dir-2640-Us Firmware.

## How do I fix CVE-2021-20134?

No fix has been published for CVE-2021-20134 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20134 being exploited?

There is no known exploitation of CVE-2021-20134 in the wild and no public exploit code.

## Other vulnerabilities in Quagga Services on D-Link DIR-2640 Routers

- [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-2021-34203](https://insights.sbomify.com/CVE-2021-34203/): Hardcoded credentials in n/a (high 8.1)
- [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-2021-20134 and fix it if it is affected.

What it is: CVE-2021-20134 is a high-severity path traversal vulnerability in Quagga Services on D-Link DIR-2640 Routers, published on 30 Dec 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-2021-20134 in the wild and no public exploit code.

Affected product: Quagga Services on D-Link DIR-2640 Routers. 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-2021-20134/ (Markdown: https://insights.sbomify.com/CVE-2021-20134/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20134
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20134
- OSV: https://osv.dev/vulnerability/CVE-2021-20134

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20134/
Summaries are generated and may contain mistakes; the official description above is the record.