# CVE-2021-34861: Memory corruption in DAP-2020

> Network-adjacent attackers can execute arbitrary code as root on D-Link DAP-2020 routers via a stack buffer overflow in the webproc endpoint.

- **Severity:** High 8.8 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 25 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-3gm8-9xxm-pmhh

## What is CVE-2021-34861?

CVE-2021-34861 is a high-severity memory corruption vulnerability in D-Link DAP-2020, published on 25 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of D-Link DAP-2020 1.01rc001 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the webproc endpoint, which listens on TCP port 80 by default. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12104.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2021-34861?

It affects 1 product.


Products: Dlink Dap-2020 Firmware.

## How do I fix CVE-2021-34861?

No fix has been published for CVE-2021-34861 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34861 being exploited?

There is no known exploitation of CVE-2021-34861 in the wild and no public exploit code.

## Other vulnerabilities in D-Link DAP-2020

- [CVE-2021-34862](https://insights.sbomify.com/CVE-2021-34862/): Memory corruption in DAP-2020 (high 8.8)
- [CVE-2021-34863](https://insights.sbomify.com/CVE-2021-34863/): Memory corruption in DAP-2020 (high 8.8)
- [CVE-2021-27248](https://insights.sbomify.com/CVE-2021-27248/): Memory corruption in DAP-2020 (high 8.8)
- [CVE-2021-27249](https://insights.sbomify.com/CVE-2021-27249/): Command injection in DAP-2020 (high 8.8)
- [CVE-2021-34860](https://insights.sbomify.com/CVE-2021-34860/): Path traversal in DAP-2020 (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34861 and fix it if it is affected.

What it is: CVE-2021-34861 is a high-severity memory corruption vulnerability in D-Link DAP-2020, published on 25 Oct 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-2021-34861 in the wild and no public exploit code.

Affected product: D-Link DAP-2020. 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-2021-34861/ (Markdown: https://insights.sbomify.com/CVE-2021-34861/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34861
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34861
- OSV: https://osv.dev/vulnerability/CVE-2021-34861

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34861/
Summaries are generated and may contain mistakes; the official description above is the record.