# CVE-2020-1685: Junos OS: EX4600, QFX5K Series: Stateless firewall filter matching 'user-vlan-id' will cause incomplete discard action

> Attackers can bypass firewall filters on Juniper switches using VXLAN, allowing unauthorized traffic to pass through interfaces.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-8m64-wrm2-jj3m

## What is CVE-2020-1685?

CVE-2020-1685 is a medium-severity vulnerability in Juniper Junos, published on 16 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

When configuring stateless firewall filters in Juniper Networks EX4600 and QFX 5000 Series devices using Virtual Extensible LAN protocol (VXLAN), the discard action will fail to discard traffic under certain conditions. Given a firewall filter configuration similar to: family ethernet-switching { filter L2-VLAN { term ALLOW { from { user-vlan-id 100; } then { accept; } } term NON-MATCH { then { discard; } } when there is only one term containing a 'user-vlan-id' match condition, and no other terms in the firewall filter except discard, the discard action for non-matching traffic will only discard traffic with the same VLAN ID specified under 'user-vlan-id'. Other traffic (e.g. VLAN ID 200) will not be discarded. This unexpected behavior can lead to unintended traffic passing through the interface where the firewall filter is applied. This issue only affects systems using VXLANs. This issue affects Juniper Networks Junos OS on QFX5K Series: 18.1 versions prior to 18.1R3-S7, except 18.1R3; 18.2 versions prior to 18.2R2-S7, 18.2R3-S1; 18.3 versions prior to 18.3R1-S5, 18.3R2-S4, 18.3R3; 18.4 versions prior to 18.4R1-S7, 18.4R2-S1, 18.4R3; 19.1 versions prior to 19.1R1-S5, 19.1R2; 19.2 versions prior to 19.2R1-S5, 19.2R2.

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2020-1685?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1685?

No fix has been published for CVE-2020-1685 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1685 being exploited?

There is no known exploitation of CVE-2020-1685 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-2020-1685 and fix it if it is affected.

What it is: CVE-2020-1685 is a medium-severity vulnerability in Juniper Junos, published on 16 Oct 2020. 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-2020-1685 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-2020-1685/ (Markdown: https://insights.sbomify.com/CVE-2020-1685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1685
- OSV: https://osv.dev/vulnerability/CVE-2020-1685

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1685/
Summaries are generated and may contain mistakes; the official description above is the record.