# CVE-2020-1668: Junos OS: EX2300 Series: High CPU load due to receipt of specific multicast packets on layer 2 interface

> Attackers can cause high CPU load and traffic interruption on Juniper EX2300 switches by sending specific multicast packets to layer 2 interfaces.

- **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-mgw6-w847-57fr

## What is CVE-2020-1668?

CVE-2020-1668 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 EX2300 Series, receipt of a stream of specific multicast packets by the layer2 interface can cause high CPU load, which could lead to traffic interruption. This issue occurs when multicast packets are received by the layer 2 interface. To check if the device has high CPU load due to this issue, the administrator can issue the following command: user@host> show chassis routing-engine Routing Engine status: ... Idle 2 percent the "Idle" value shows as low (2 % in the example above), and also the following command: user@host> show system processes summary ... PID USERNAME PRI NICE SIZE RES STATE TIME WCPU COMMAND 11639 root 52 0 283M 11296K select 12:15 44.97% eventd 11803 root 81 0 719M 239M RUN 251:12 31.98% fxpc{fxpc} the eventd and the fxpc processes might use higher WCPU percentage (respectively 44.97% and 31.98% in the above example). This issue affects Juniper Networks Junos OS on EX2300 Series: 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 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 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-S2, 20.1R2.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-1668?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1668?

No fix has been published for CVE-2020-1668 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1668 being exploited?

There is no known exploitation of CVE-2020-1668 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-2020-1668 and fix it if it is affected.

What it is: CVE-2020-1668 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-2020-1668 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-2020-1668/ (Markdown: https://insights.sbomify.com/CVE-2020-1668/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1668
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1668
- OSV: https://osv.dev/vulnerability/CVE-2020-1668

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1668/
Summaries are generated and may contain mistakes; the official description above is the record.