# CVE-2020-3427: Duo Authentication for Windows Logon and RDP Privilege Escalation Vulnerability

> Local attackers can exploit path validation flaws in the installer to write to privileged directories, potentially achieving privilege escalation or causing denial of service.

- **Severity:** Medium 6.6 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 14 Oct 2020
- **Updated:** 13 Nov 2024
- **Also known as:** GHSA-437m-6wfg-j372

## What is CVE-2020-3427?

CVE-2020-3427 is a medium-severity path traversal vulnerability in Cisco Duo Authentication for Windows Logon and RDP, published on 14 Oct 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The Windows Logon installer prior to 4.1.2 did not properly validate file installation paths. This allows an attacker with local user privileges to coerce the installer to write to arbitrary privileged directories. If successful, an attacker can manipulate files used by Windows Logon, cause Denial of Service (DoS) by deleting file(s), or replace system files to potentially achieve elevation of privileges. Note that this can only exploitable during new installations while the installer is running and is not exploitable once installation is finished. Versions 4.1.2 of Windows Logon addresses this issue.

Weakness: CWE-280 (Improper Handling of Insufficient Permissions or Privileges)

## Which versions are affected by CVE-2020-3427?

It affects 1 product.


Products: Cisco Duo Authentication for Windows Logon and Rdp.

## How do I fix CVE-2020-3427?

No fix has been published for CVE-2020-3427 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3427 being exploited?

There is no known exploitation of CVE-2020-3427 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Duo Authentication for Windows Logon and RDP

- [CVE-2024-20301](https://insights.sbomify.com/CVE-2024-20301/): Auth bypass in Cisco Duo (medium 6.2)
- [CVE-2024-20292](https://insights.sbomify.com/CVE-2024-20292/): Information disclosure in Cisco Duo (medium 4.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3427 and fix it if it is affected.

What it is: CVE-2020-3427 is a medium-severity path traversal vulnerability in Cisco Duo Authentication for Windows Logon and RDP, published on 14 Oct 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-3427 in the wild and no public exploit code.

Affected product: Cisco Duo Authentication for Windows Logon and RDP. 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-2020-3427/ (Markdown: https://insights.sbomify.com/CVE-2020-3427/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3427
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3427
- OSV: https://osv.dev/vulnerability/CVE-2020-3427

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-3427/
Summaries are generated and may contain mistakes; the official description above is the record.