# CVE-2020-20021: Denial of service in n/a

> An attacker can cause a denial of service on MikroTik routers by exploiting a misconfiguration in the SSH daemon.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 12 Jul 2023
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-x6pw-rqmx-w72p

## What is CVE-2020-20021?

CVE-2020-20021 is a high-severity denial of service vulnerability in Mikrotik Routeros, published on 12 Jul 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue discovered in MikroTik Router v6.46.3 and earlier allows attacker to cause denial of service via misconfiguration in the SSH daemon.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-20021?

It affects 1 product.


Products: Mikrotik Routeros.

## How do I fix CVE-2020-20021?

No fix has been published for CVE-2020-20021 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-20021 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-20021 exists.

## Other vulnerabilities in Mikrotik Routeros

- [CVE-2018-7445](https://insights.sbomify.com/CVE-2018-7445/): MikroTik RouterOS Stack-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2026-86060](https://insights.sbomify.com/CVE-2026-86060/): MikroTik RouterOS Improper Neutralization of Argument Delimiters in a Command (critical 9.2, exploited in the wild)
- [CVE-2018-14847](https://insights.sbomify.com/CVE-2018-14847/): MikroTik Router OS Directory Traversal (critical 9.1, exploited in the wild)
- [CVE-2026-67277](https://insights.sbomify.com/CVE-2026-67277/): MikroTik RouterOS Missing Authentication for Critical Function (high 8.8, exploited in the wild)
- [CVE-2026-67279](https://insights.sbomify.com/CVE-2026-67279/): Mikrotik RouterOS Improper Enforcement of Behavioral Workflow (medium 6.9, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-20021 and fix it if it is affected.

What it is: CVE-2020-20021 is a high-severity denial of service vulnerability in Mikrotik Routeros, published on 12 Jul 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-20021 exists.

Affected product: Mikrotik Routeros. 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-2020-20021/ (Markdown: https://insights.sbomify.com/CVE-2020-20021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-20021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-20021
- OSV: https://osv.dev/vulnerability/CVE-2020-20021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-20021/
Summaries are generated and may contain mistakes; the official description above is the record.