# CVE-2019-3981: Weak cryptography in WinBox

> Man-in-the-middle attackers can downgrade authentication to recover user credentials, requiring users to upgrade the Winbox client.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Jan 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-pg5r-4rf5-r7hv

## What is CVE-2019-3981?

CVE-2019-3981 is a low-severity vulnerability in Mikrotik Routeros, published on 14 Jan 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

MikroTik Winbox 3.20 and below is vulnerable to man in the middle attacks. A man in the middle can downgrade the client's authentication protocol and recover the user's username and MD5 hashed password.

Weakness: CWE-300 (Channel Accessible by Non-Endpoint)

## Which versions are affected by CVE-2019-3981?

It affects 2 products.


Products: Mikrotik Routeros, Mikrotik Winbox.

## How do I fix CVE-2019-3981?

No fix has been published for CVE-2019-3981 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-3981 being exploited?

There is no known exploitation of CVE-2019-3981 in the wild and no public exploit code.

## 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-2019-3981 and fix it if it is affected.

What it is: CVE-2019-3981 is a low-severity vulnerability in Mikrotik Routeros, published on 14 Jan 2020. 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-2019-3981 in the wild and no public exploit code.

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-2019-3981/ (Markdown: https://insights.sbomify.com/CVE-2019-3981/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-3981
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-3981
- OSV: https://osv.dev/vulnerability/CVE-2019-3981

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-3981/
Summaries are generated and may contain mistakes; the official description above is the record.