# CVE-2020-1687: Denial of service in Junos OS

> Attackers can cause high CPU load and traffic interruption on Juniper switches by sending specific VXLAN frames in EVPN deployments.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-pvh5-g247-37mv

## What is CVE-2020-1687?

CVE-2020-1687 is a medium-severity denial of service vulnerability in Juniper Junos, published on 16 Oct 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

On Juniper Networks EX4300-MP Series, EX4600 Series and QFX5K Series deployed in (Ethernet VPN) EVPN-(Virtual Extensible LAN) VXLAN configuration, receipt of a stream of specific VXLAN encapsulated layer 2 frames can cause high CPU load, which could lead to network protocol operation issue and traffic interruption. This issue affects devices that are configured as a Layer 2 or Layer 3 gateway of an EVPN-VXLAN deployment. The offending layer 2 frames that cause the issue originate from a different access switch that get encapsulated within the same EVPN-VXLAN domain. This issue affects Juniper Networks Junos OS on EX4300-MP Series, EX4600 Series and QFX5K Series: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R2-S5, 18.4R3-S4; 19.1 versions prior to 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 19.2R3; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S3, 20.1R2.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-1687?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1687?

No fix has been published for CVE-2020-1687 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1687 being exploited?

There is no known exploitation of CVE-2020-1687 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos

- [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild)
- [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild)
- [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild)
- [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild)
- [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1687 and fix it if it is affected.

What it is: CVE-2020-1687 is a medium-severity denial of service vulnerability in Juniper Junos, published on 16 Oct 2020. 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-2020-1687 in the wild and no public exploit code.

Affected product: Juniper Junos. 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-2020-1687/ (Markdown: https://insights.sbomify.com/CVE-2020-1687/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1687
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1687
- OSV: https://osv.dev/vulnerability/CVE-2020-1687

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1687/
Summaries are generated and may contain mistakes; the official description above is the record.