# CVE-2019-0041: Junos OS: EX4300-MP Series: IP transit traffic can reach the control plane via loopback interface.

> Attackers can bypass loopback filters to reach the control plane on Juniper EX4300-MP switches, potentially causing service disruption.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Apr 2019
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-5jhv-p44r-72j3

## What is CVE-2019-0041?

CVE-2019-0041 is a medium-severity vulnerability in Juniper Junos, published on 10 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On EX4300-MP Series devices with any lo0 filters applied, transit network traffic may reach the control plane via loopback interface (lo0). The device may fail to forward such traffic. This issue affects Juniper Networks Junos OS 18.2 versions prior to 18.2R1-S2, 18.2R2 on EX4300-MP Series. This issue does not affect any other EX series devices.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2019-0041?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2019-0041?

No fix has been published for CVE-2019-0041 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-0041 being exploited?

There is no known exploitation of CVE-2019-0041 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-2019-0041 and fix it if it is affected.

What it is: CVE-2019-0041 is a medium-severity vulnerability in Juniper Junos, published on 10 Apr 2019. 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-2019-0041 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-2019-0041/ (Markdown: https://insights.sbomify.com/CVE-2019-0041/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-0041
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-0041
- OSV: https://osv.dev/vulnerability/CVE-2019-0041

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-0041/
Summaries are generated and may contain mistakes; the official description above is the record.