# CVE-2020-1666: Junos OS Evolved: 'console log-out-on-disconnect' fails to terminate session on console cable disconnection

> Attackers with physical console access can resume active sessions due to failed logout on disconnect, potentially gaining administrative privileges.

- **Severity:** Medium 6.6 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** No
- **Published:** 16 Oct 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-62gf-43c6-cfmp

## What is CVE-2020-1666?

CVE-2020-1666 is a medium-severity authentication bypass vulnerability in Juniper Junos Os Evolved, published on 16 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 system console configuration option 'log-out-on-disconnect' In Juniper Networks Junos OS Evolved fails to log out an active CLI session when the console cable is disconnected. This could allow a malicious attacker with physical access to the console the ability to resume a previous interactive session and possibly gain administrative privileges. This issue affects all Juniper Networks Junos OS Evolved versions after 18.4R1-EVO, prior to 20.2R1-EVO.

Weakness: CWE-613 (DEPRECATED: Insufficient Session Expiration), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2020-1666?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2020-1666?

No fix has been published for CVE-2020-1666 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1666 being exploited?

There is no known exploitation of CVE-2020-1666 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos Os Evolved

- [CVE-2026-21902](https://insights.sbomify.com/CVE-2026-21902/): Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root (critical 9.3)
- [CVE-2023-28983](https://insights.sbomify.com/CVE-2023-28983/): Junos OS Evolved: Shell Injection vulnerability in the gNOI server (high 8.8)
- [CVE-2025-21599](https://insights.sbomify.com/CVE-2025-21599/): Denial of service in Junos OS Evolved (high 8.7)
- [CVE-2024-47502](https://insights.sbomify.com/CVE-2024-47502/): Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS (high 8.7)
- [CVE-2024-39531](https://insights.sbomify.com/CVE-2024-39531/): Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1666 and fix it if it is affected.

What it is: CVE-2020-1666 is a medium-severity authentication bypass vulnerability in Juniper Junos Os Evolved, published on 16 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-2020-1666 in the wild and no public exploit code.

Affected product: Juniper Junos Os Evolved. 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-2020-1666/ (Markdown: https://insights.sbomify.com/CVE-2020-1666/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1666
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1666
- OSV: https://osv.dev/vulnerability/CVE-2020-1666

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-1666/
Summaries are generated and may contain mistakes; the official description above is the record.