# CVE-2020-1671: Junos OS: Receipt of malformed DHCPv6 packets causes jdhcpd to crash.

> Malformed DHCPv6 packets crash the JDHCPD daemon on Junos OS devices configured as DHCPv6 servers or relays, causing service disruption.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2020
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-cx8w-wg7g-8xjv

## What is CVE-2020-1671?

CVE-2020-1671 is a high-severity denial of service 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

On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash with a core dump if a malformed DHCPv6 packet is received, resulting with the restart of the daemon. This issue only affects DHCPv6, it does not affect DHCPv4. This issue affects: Juniper Networks Junos OS 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.2X75 versions prior to 18.2X75-D65; 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; 19.2 version 19.2R2 and later versions; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R1-S3, 20.1R2; This issue does not affect Juniper Networks Junos OS prior to 17.4R1.

Weakness: CWE-125 (Out-of-bounds Read), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2020-1671?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1671?

No fix has been published for CVE-2020-1671 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1671 being exploited?

There is no known exploitation of CVE-2020-1671 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-2020-1671 and fix it if it is affected.

What it is: CVE-2020-1671 is a high-severity denial of service 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-2020-1671 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-2020-1671/ (Markdown: https://insights.sbomify.com/CVE-2020-1671/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1671
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1671
- OSV: https://osv.dev/vulnerability/CVE-2020-1671

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1671/
Summaries are generated and may contain mistakes; the official description above is the record.