# CVE-2020-1672: Junos OS: jdhcpd process crash when processing a specific DHCPDv6 packet in DHCPv6 relay configuration.

> Attackers can cause a persistent denial of service on Juniper devices by sending crafted DHCPv6 packets when relay is enabled.

- **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:** 16 Sep 2024
- **Also known as:** GHSA-44r3-5r2m-3rw8

## What is CVE-2020-1672?

CVE-2020-1672 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 devices configured with DHCPv6 relay enabled, receipt of a specific DHCPv6 packet might crash the jdhcpd daemon. The jdhcpd daemon automatically restarts without intervention, but continuous receipt of specific crafted DHCP messages will repeatedly crash jdhcpd, leading to an extended Denial of Service (DoS) condition. Only DHCPv6 packet can trigger this issue. DHCPv4 packet cannot trigger this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2, 17.4R3-S3; 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 19.1R2-S2, 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R2-S1, 19.2R3; 19.3 versions prior to 19.3R2-S4, 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-S3, 20.1R2.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2020-1672?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2020-1672?

No fix has been published for CVE-2020-1672 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1672 being exploited?

There is no known exploitation of CVE-2020-1672 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-2020-1672 and fix it if it is affected.

What it is: CVE-2020-1672 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-2020-1672 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-2020-1672/ (Markdown: https://insights.sbomify.com/CVE-2020-1672/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1672
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1672
- OSV: https://osv.dev/vulnerability/CVE-2020-1672

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1672/
Summaries are generated and may contain mistakes; the official description above is the record.