# CVE-2020-1681: Junos OS Evolved: Receipt of a specifically malformed NDP packet could lead to Denial of Service

> Attackers can cause a denial of service in Junos OS Evolved by sending malformed NDP packets, crashing the ndp process.

- **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-w8cp-6x5g-mf2j

## What is CVE-2020-1681?

CVE-2020-1681 is a medium-severity denial of service vulnerability in Juniper Junos Os Evolved, 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

Receipt of a specifically malformed NDP packet sent from the local area network (LAN) to a device running Juniper Networks Junos OS Evolved can cause the ndp process to crash, resulting in a Denial of Service (DoS). The process automatically restarts without intervention, but a continuous receipt of the malformed NDP packets could leaded to an extended Denial of Service condition. During this time, IPv6 neighbor learning will be affected. The issue occurs when parsing the incoming malformed NDP packet. Rather than simply discarding the packet, the process asserts, performing a controlled exit and restart, thereby avoiding any chance of an unhandled exception. Exploitation of this vulnerability is limited to a temporary denial of service, and cannot be leveraged to cause additional impact on the system. This issue is limited to the processing of IPv6 NDP packets. IPv4 packet processing cannot trigger, and is unaffected by this vulnerability. This issue affects all Juniper Networks Junos OS Evolved versions prior to 20.1R2-EVO. Junos OS is unaffected by this vulnerability.

Weakness: CWE-617 (Reachable Assertion), CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2020-1681?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2020-1681?

No fix has been published for CVE-2020-1681 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1681 being exploited?

There is no known exploitation of CVE-2020-1681 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-2020-1681 and fix it if it is affected.

What it is: CVE-2020-1681 is a medium-severity denial of service vulnerability in Juniper Junos Os Evolved, 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-2020-1681 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-2020-1681/ (Markdown: https://insights.sbomify.com/CVE-2020-1681/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1681
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1681
- OSV: https://osv.dev/vulnerability/CVE-2020-1681

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-1681/
Summaries are generated and may contain mistakes; the official description above is the record.